Multiplexing schemes for ofdma

ABSTRACT

Methods and systems are provided for allocating resources including VoIP (voice over Internet Protocol) and Non-VoIP resources. In some embodiments, multiplexing schemes are provided for use with OFDMA (orthogonal frequency division multiplexing access) systems, for example for use in transmitting VoIP traffic. In some embodiments, various HARQ (Hybrid Automatic request) techniques are provided for use with OFDMA systems. In various embodiments, there are provided methods and systems for dealing with issues such as Handling non-full rate vocoder frames, VoIP packet jitter handling, VoIP capacity increasing schemes, persistent and non-persistent assignment of resources in OFDMA systems.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.12/090,964, filed on Oct. 6, 2008, which claims the benefit of U.S.Provisional Application Nos.

60/805,670 filed Jun. 23, 2006,

60/820,683 filed Jul. 28, 2006,

60/822,018 filed Aug. 10, 2006,

60/824,848 filed Sep. 7, 2006,

60/825,360 filed Sep. 12, 2006,

60/828,312, filed Oct. 5, 2006

60/728,848 filed Oct. 21, 2005,

60/820,705 filed Jul. 28, 2006,

60/758,743 filed Jan. 13, 2006, and

60/829,426 filed Oct. 12, 2006, which are all incorporated herein byreference as if set forth fully and completely herein.

FIELD OF THE INVENTION

The invention relates to multiplexing schemes for use with OFDMA(orthogonal frequency division multiplexing access) systems, for examplefor use in transmitting VoIP (voice over Internet Protocol) traffic.

BACKGROUND OF THE INVENTION

There are several proposals to 3GPP2 for OFDMA VoIP implementations, oneof which defines numerology such that an OFDMA resource consisting of aset of 340 sub-carriers in frequency over OFDM symbol durations in timeis divided into 20 ms VoIP frames, each containing 24 slots, each slotcontaining 10 OFDM symbols. The resources of each slot are furthersubdivided into distributed resource channels (DRCH), each comprising 81subcarrier locations distributed across the 10 symbols of a slot for atotal of 40 DRCHs per slot allowing for pilots and other overhead thatmight be present.

Transmission for a given user occurs at different rates or frame sizes.For example, the EVRC (Enhanced Variable Rate Codec) codec generatesvoice frames with four different rates or frame sizes: full, ½, ¼ and ⅛with probabilities of 29%, 4%, 7% and 60% respectively. The particularrate is typically determined as a function of a voice activity factor.

For a given user, a single packet is nominally expected to be deliveredwithin one VoIP frame. Current definitions allow for an initial attemptto deliver the packet and three subsequent attempts. Any attempt,including the initial or subsequent, is referred to herein as asub-packet.

A few variations of H-ARQ transmission/operation schemes exist. Onevariation is unicast H-ARQ in which each encoded packet includes datafrom one user. This can be fully asynchronous in which case themodulation and code rate (MCS (modulation and coding scheme),transmission time (slot/frame) and resource allocation are independentfor each transmission of an encoded packet (first and allre-transmissions). Assignment signalling is used to describe theresource allocation, MCS and user IDs for each transmission andre-transmission. While this approach allows adaptation to real timechannel conditions, it incurs large signalling overhead. Unicast H-ARQcan alternatively be fully synchronous. In this case, the MCS scheme fortransmissions (first and all retransmissions) is the same, resourceallocation (location) remains the same for first and all retransmissions(the transmission location must be the same as the first transmission).The transmission interval is fixed, and assignment signalling isrequired only for the first transmission. This enables lower signallingoverhead for retransmission, but can cause significant schedulingcomplexity and signalling overhead for the first transmission due to theirregular vacancies of resources that occurs since some resources needto be reserved for retransmissions that may not be necessary.

Another H-ARQ variant is multicast H-ARQ in which each encoded packetincludes data for multiple users. The worst CQIs (channel qualityindicators) among multiple users are considered for selecting MCS. Theentire packet is retransmitted if one or more users could not decode itsuccessfully, even though some of the users may have successfullydecoded the packet. Multi-cast H-ARQ can be implemented using fullyasynchronous and fully synchronous schemes.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodcomprising: transmitting full rate vocoder frames using an amount ofOFDM time/frequency resource; for at least one non-full rate vocoderframe, transmitting a first sub-packet transmission of each non-fullrate vocoder frame using the same amount of OFDM time/frequency resourceas used for full rate vocoder frames; matching vocoder frame size to theamount of OFDMA time/frequency resource by employing an increased codingrate (compared to the full rate frame) and/or repetition factor.

In some embodiments the method further comprises using resources freedup due to a higher probability of success for first sub-packettransmission of non-full rate frames for allocation to other wirelessstations.

In some embodiments the different coding rate and/or repetition factorused for full rate, and non-full rate are predetermined and known to awireless station.

In some embodiments the method is applied for downlink transmission froma base station to a plurality of wireless stations, the method furthercomprising: at least one wireless station using blind rate detection todetect an actual frame rate transmitted by the base station.

In some embodiments the at least one non-full rate comprises rates ½ and¼.

According to a second aspect of the invention, there is provided amethod comprising: persistently allocating an OFDM transmission resourceto a wireless station; blanking a minimum rate sub-packet within thepersistently allocated OFDM transmission resource; and using the unusedretransmission resource for allocation to other wireless stations.

In some embodiments the method is applied for downlink transmission froma base station to a plurality of wireless stations, the method furthercomprising: the base station receiving a NAK from the wireless stationin response to blanking the sub-packet; the base station echoing receiptof the NAK with an ACK to indicate no resource is being assigned forretransmission.

In some embodiments echoing receipt of the NAK with an ACK to indicateno resource is being assigned for retransmission to that wirelessstation comprises transmitting an ACK-NAK-echo bitmap indicating ACK/NAKstatus.

In some embodiments the method further comprises transmitting keep-alivereduced rate frames.

In some embodiments the method further comprises: using a same amount offrequency/time resource for the minimum rate frames as for full rateframes so as to increase probability of successful transmission, andusing freed up retransmission resources for allocation to other wirelessstations.

In some embodiments the minimum rate is ⅛ rate.

According to a third aspect of the invention, there is provided a methodof transmitting sub-packets within VoIP frames comprising: persistentlyallocating a resource to a wireless station while there are non-blankedsub-packets to send/receive to/from that wireless station; when thereare no non-blanked sub-packets to send/receive for a given wirelessstation, re-assigning the unused resource to other wireless stations, ora different data stream for the same wireless station, in anon-persistent manner.

In some embodiments the resource assignment is identified by specificresource/channel/node index or OFDMA sub-carrier and symbol indices.

In some embodiments the method is applied for downlink transmission froma base station to a plurality of wireless stations, the method furthercomprising: an original wireless station with a persistent allocation ofthe blanked transmission decoding the sub-packet transmitted on itspersistent resource allocation, and if successfully decoded using alayer 2 protocol to detect a mismatch on a user ID and discarding thesub-packet; the base station ignoring any HARQ ACK/NAK received from theoriginal wireless station with the persistent allocation.

In some embodiments the method further comprises: if the wirelessstation with the non-persistent allocation occupying the unusedpersistent resource does not require HARQ retransmission, at theretransmission slot, the transmitter sending an ACK indication toindicate there is no resource assigned to the wireless station with thepersistent allocation for HARQ transmission; using an unusedretransmission resource for other wireless stations.

In some embodiments sending an ACK indication comprises setting acorresponding bit in a ACK-NAK-echo bitmap to ‘ACK’.

In some embodiments the method is applied for downlink transmission froma base station to a plurality of wireless stations, the method furthercomprising, if the wireless station with the non-persistent allocationoccupying the unused persistent resource requires HARQ retransmission:retransmitting the sub-packet for the wireless station with thenon-persistent allocation using a different resource than the previoussub-packet, and explicitly signalling the new resource; the transmittersending an ACK indication in respect of the persistently allocatedresource; reallocating the unused persistently allocated resource forother wireless stations.

In some embodiments the method is applied for downlink transmission froma base station to a plurality of wireless stations, the method furthercomprising, if the wireless station with the non-persistently allocatedresource occupying the unused persistent resource requires HARQretransmission: retransmitting the sub-packet for the wireless stationwith the non-persistently allocated resource using the same resource asthe previous sub-packet without using any explicit signalling for theretransmission; the transmitter setting an ACK indicator to ‘NAK’ toindicate that a resource assigned to the wireless station with thepersistent allocation is being used for retransmission.

According to a fourth aspect of the invention, there is provided amethod of transmitting OFDM signals containing sub-packets within framescomprising: if there is no packet for a given wireless station at aframe boundary, blanking a persistent allocation for that wirelessstation; allocating blanked resources to other wireless stations.

In some embodiments the frames are VoIP frames and a frame boundary is aVoIP frame boundary.

In some embodiments the method further comprises delivering a packetthat arrives after the VoIP frame boundary by: transmitting a sub-packetfor the packet in a lower MCS format intended for a reduced number ofretransmission trials.

In some embodiments the method further comprises delaying packetsarriving after a predefined number of retransmission slots until thenext VoIP frame.

In some embodiments the method further comprises delivering a packetthat arrives after the VoIP frame boundary by: delaying the packettransmission until the next VoIP frame; combining delayed and currentVoIP packets into a composite packet.

In some embodiments the method further comprises: supplementing apersistent allocation with additional non-persistent resources for thenext VoIP frame.

In some embodiments the method further comprises transmitting thecomposite packet using assigned persistent resources by changing the MCSaccordingly.

In some embodiments the method further comprises using the “missedframe” to trigger blind detection of MCS for the composite packet in thenext frame.

In some embodiments the method further comprises delivering a packetthat arrives after the VoIP frame boundary by: delaying the packettransmission until resources become available; continuing to sendpackets in sequence without combining multiple voice packets intocomposite packets; emptying a layer 2 buffer during blanked transmissiontimes.

In some embodiments the method further comprises a base station adding a‘de-jitter’ delay to every VoIP packet that arrives at the layer 2buffer such that the probability of a packet available at every VoIPframe boundary is above a predefined threshold.

According to a fifth aspect of the invention, there is provided a methodof transmitting sub-packets within frames comprising: transmittingframes using OFDM, each frame occupying a plurality of OFDM symbols;allocating first sub-packet transmission for a set of wireless stationsin a staggered manner throughout a frame.

In some embodiments the frames are VoIP frames and a frame boundary is aVoIP frame boundary.

In some embodiments each VoIP frame is comprised of a plurality of slotseach containing a respective plurality of OFDM symbols and whereinallocating first sub-packet transmission for a set of wireless stationsin a staggered manner throughout a VoIP frame comprises allocating firstsub-packet transmission on an approximately statistically equal basisacross slots of the VoIP frame.

According to a sixth aspect of the invention, there is provided a methodof transmitting sub-packets within frames comprising: transmittingframes using OFDM, each occupying a plurality of OFDM symbols; dividingwireless stations into a plurality of different classes, each classhaving a respective different number of maximum HARQ retransmissionssuch that wireless stations with more reliable CQI estimates are groupedtogether and allowed fewer re-transmissions; transmitting the framescontaining first sub-packets and retransmission sub-packets subject tothe maximum number of HARQ retransmissions for each wireless station.

In some embodiments the frames are VoIP frames and a frame boundary is aVoIP frame boundary.

In some embodiments the method further comprises: if a packet failsafter a reduced number of transmissions, the wireless station sending aNAK: if that wireless station is intended to have only the reducednumber of transmissions the transmitter sets an ACK indicator to ‘ACK’to indicate no further resource is being allocated for the remainder ofthe frame such that it is not necessary to signal to each wirelessstation what class the wireless station belongs to.

According to a seventh aspect of the invention, there is provided amethod of transmitting sub-packets within frames comprising:transmitting frames using OFDM, each frame occupying a plurality of OFDMsymbols; for some wireless stations, allocating resources over multiplesof nominal frames; for wireless stations being allocated resources overmultiples of nominal frames, combining multiple packets into compositepackets, and allocating these composite packets with a larger number ofretransmissions for improved reliability.

According to an eighth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; for some wireless stations, allocatingresources over multiples of nominal frames; for some wireless stations,transmitting an original sub-packet for a first packet during a firstframe, with retransmission sub-packets following as necessary;transmitting a next original sub-packet for another packet for thatwireless station immediately, possibly during the first frame, followingthe successful reception of the first packet, with retransmissions asnecessary which may cross a frame boundary.

In some embodiments the frames are VoIP frames.

According to a ninth aspect of the invention, there is provided a methodof transmitting sub-packets within frames comprising: transmittingframes using OFDM, each frame occupying a plurality of OFDM symbols;transmitting to each wireless station with a respective resourceallocation size, and a respective MCS; implicitly indicating MCS to eachreceiver by employing a unique mapping of MCS to resource allocationsize.

In some embodiments the frames are VoIP frames.

In some embodiments the following MCS to resource allocation sizemapping is employed:

QPSK, code rate 1/3—first resource allocation size;QPSK, code rate 2/3—second resource allocation size;16 QAM, code rate 2/3—third resource allocation size.

According to a tenth aspect of the invention, there is provided a methodcomprising: for nominal operating conditions, transmitting anACK-NAK-echo bitmap or any type of ACK/NAK echo echoing the NAK(s) orACK(s) sent by one or more wireless stations; in some instances,transmitting the ACK-NAK-echo bitmap with an ACK to echo a NAKtransmitted by the wireless station, or with an NAK to echo an ACKtransmitted by the wireless station for the purpose of signallingsomething to the wireless station.

According to an eleventh aspect of the invention, there is provided amethod of performing resource assignment comprising: sending a bitmap(or other signalling) containing a respective location for each of aplurality of wireless stations, with each wireless station's relativeposition in the bitmap (or other signalling) being associated with someOFDM resource allocation; wherein a value at a position in the bitmap(or other signalling), indicates whether or not a resource has beenassigned to the receiver associated with that bitmap (or othersignalling) position.

In some embodiments for at least some wireless stations, the bitmap (orother signalling) allows each wireless station that has been assigned anon-persistent resource to derive what resource has beennon-persistently assigned.

In some embodiments a persistent allocation is used for a firsttransmission for each wireless station.

In some embodiments the relative wireless station' positions in thebitmap (or other signalling) are also associated with a group ofwireless stations, such that wireless stations belonging to a specificgroup can be uniquely identified by their position in the bitmap (orother signalling).

In some embodiments the wireless stations of a given group includewireless stations that have their first HARQ sub-packet transmissionoccurring in the same slot within a HARQ interlace.

In some embodiments the method further comprises transmitting multiplebitmaps (or other signalling), and assigning wireless stations to acommon bitmap (or other signalling) on the basis of commonality amongfactors such as long-term channel condition, modulation and codingscheme (MCS), resource allocation size, etc.

In some embodiments the bitmap (or other signalling) positions fordifferent wireless stations in the same group are separated by the totalof possible start points for a given HARQ interlace.

In some embodiments the bitmap (or other signalling) positions fordifferent wireless stations in the same group are separated by a totalnumber of transmissions allowed per sub-packet.

In some embodiments the bitmap is used to indicate non-persistentassignments.

In some embodiments the method comprises at a transmitter or otherelement where allocation is being performed: creating the bitmap (orother signalling) indicating which wireless station will be assignedresources in the an allocation period; the bitmap (or other signalling)is processed by starting at the position of the first wireless stationof a first group of wireless stations; if indicated by the bitmap (orother signalling), the first resource is allocated to this wirelessstation whereas if the bitmap (or other signalling) does not indicate aresource allocation to the wireless station, the resource is availableto be assigned to the next wireless station; the next position processesis that of the second wireless station belonging to the first group ofwireless stations; if the first resource was assigned via the bitmap (orother signalling) in the previous step, the next resource (second) isassigned to this wireless station whereas if resources were not assignedto the first wireless station, then the second wireless station isassigned the first resource; each wireless station from the first groupof wireless stations is assigned resources in this manner.

In some embodiments the method further comprises adding further groupsof wireless stations to the bitmap (or other signalling), each furthergroup being assigned resources in the manner as the first with thosewireless stations assigned resources will occupy the “next” resourcesafter the last assigned resources, this process continuing until allwireless stations from all groups have been processed.

In some embodiments the method further comprises: defining each group ofwireless stations to be a group of wireless stations that have theirfirst HARQ sub-packet transmission during a same scheduling period;wherein the first group of wireless stations consists of wirelessstations in a group of wireless stations that is receiving its firstHARQ sub-packet transmission in the current scheduling period.

In some embodiments the method further comprises: defining a first groupof wireless stations each of which is to be allocated a respectivepersistent resource; using the bitmap (or other signalling) to indicatefor each wireless station of the first group of wireless stationswhether or not a sub-packet is to be transmitted to them on theirpersistent resource; re-assigning persistent resources that are not usedby the first to other wireless stations.

In some embodiments the first group is a different group for eachscheduling period.

In some embodiments the first group for each scheduling period is each agroup of wireless stations that have their first HARQ sub-packettransmission during that scheduling period.

In some embodiments the method further comprises: for each wirelessstation receiving a resource allocation according to the bitmap (orother signalling), transmitting at least one resource allocationparameter.

In some embodiments at least one resource allocation parameterscomprises at least one of:

resource start position;

modulation and coding scheme;

MIMO mode indication;

size indication;

ARQ channel identifier.

In some embodiments the method further comprises: grouping wirelessstations with roughly the same arriving time, and/or similar channelconditions, and/or same or similar MCS in a common bitmap (or othersignalling), identified collectively by a Group_ID.

In some embodiments the method further comprises: using a respectivesignalling channel containing resource assignments to each of aplurality of groups of wireless stations, the groups of wirelessstations being grouped according to common distance from the transmitterand/or channel conditions.

In some embodiments the method further comprises: signalling resourceallocations for HARQ retransmissions in the same manner as originaltransmissions.

In some embodiments the method further comprises: defining at least onegroup VoIP wireless stations, and one or more groups are for non-VoIPwireless stations.

In some embodiments the method further comprises: using a first set ofMCS for VoIP wireless stations, and a second set of MCS for non-VoIPwireless stations.

In some embodiments the method further comprises: transmitting a secondbitmap (or other signalling) with a respective entry for each wirelessstation assigned resources by the first bitmap to indicate if thetransmission is an original sub-packet or a re-transmission sub-packet.

In some embodiments the method further comprises: scheduling resourceallocations with a fully dynamic resource allocation.

In some embodiments the method further comprises: scheduling resourceallocations with a hybrid resource allocation that combines dynamicresource allocation and static resource allocation.

According to a twelfth aspect of the invention, there is provided amethod in a wireless station of determining its resource assignmentcomprising: receiving a bitmap (or other signalling); determiningwhether resources have been assigned to the wireless station on thebasis of the bitmap (or other signalling); if so, performing at leastone of: processing a persistent resource assignment; processing anon-persistent resource assignment determined by the position of thewireless station in the bitmap (or other signalling), and the number ofassignments to other wireless stations.

In some embodiments each wireless station is allocated a persistentresource assignment for first HARQ sub-packet transmissions with otherresource assignments being non-persistent.

In some embodiments processing a persistent resource assignmentcomprises: determining if the wireless station is to receive a resourceallocation from the bitmap (or other signalling); if the bitmap (orother signalling) indicates that wireless station is to receive aresource allocation, processing a persistently allocated resource; andprocessing a non-persistent resource assignment comprises: determiningif the wireless station is to receive a resource allocation from thebitmap (or other signalling); if the bitmap (or other signalling)indicates that wireless station is to receive a resource allocationdetermining from the bitmap (or other signalling) the resourcesallocated to persistent wireless stations and to previous allocations tonon-persistent wireless stations, and processing a next resource thathas not been allocated as the non-persistently allocated resource forthat wireless station.

In some embodiments the method further comprises adding wirelessstations to the bitmap (or other signalling) in a way that does notimpact the bitmap (or other signalling) positions of wireless stationswho have previously been assigned a position.

In some embodiments at least some new wireless stations are added to theend of the bitmap (or other signalling).

In some embodiments at least some new wireless stations are added intovacant bitmap (or other signalling) positions created by wirelessstation leaving (or being deleted from) the bitmap (or othersignalling).

In some embodiments the method further comprises: performing a temporaryallocation of resources associated with a bitmap (or other signalling)to at least one wireless station that is not part of the bitmap (orother signalling) when the resources are not all required by wirelessstations that are part of the bitmap (or other signalling).

In some embodiments performing temporary allocation of resourcesassociated with a bitmap (or other signalling) to at least one wirelessstations that is not part of the bitmap (or other signalling) comprises:determining a particular wireless station that is part of the bitmap (orother signalling) does not require resources in a given schedulingperiod and allocating the resources to at least one wireless stationthat is not part of the bitmap (or other signalling); signalling theresource allocation to the at least one wireless station that is notpart of the bitmap (or other signalling).

According to a thirteenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; performing full persistent resourceallocation for at least one wireless station by allocating resourcespersistently for both original sub-packet transmissions andretransmission sub-packets.

In some embodiments the frames are VoIP frames.

In some embodiments the method comprises: performing full persistentresource allocation for some of wireless stations and performing firsttransmission persistent allocation by allocating a resource persistentlyonly for first transmissions for remaining wireless stations.

In some embodiments the method further comprises using a combined bitmap(or other signalling) to signal resource allocation both for wirelessstations having full persistent resource allocation and for wirelessstations having first transmission persistent allocation.

In some embodiments using a combined bitmap (or other signalling) tosignal resource allocation both for wireless stations having fullpersistent resource allocation and for wireless stations having firsttransmission persistent allocation comprises: designating wirelessstations with full persistent allocation as a special user group in thebitmap (or other signalling).

In some embodiments the method further comprises segmenting wirelessstations with full persistent allocation into groups that have differentHARQ sub-packet start points.

In some embodiments the method further comprises allocating resourcelocations for the first transmission persistent allocations immediatelyafter the resource locations of the wireless stations with persistentallocation for all transmissions.

In some embodiments the method further comprises re-packing andreassigning resources that were not used by one or both of a) thewireless stations with persistent allocation for all transmissions andb) the wireless stations with persistent allocation for the firstsub-packet transmission.

In some embodiments the method further comprises: reassigned wirelessstations determining what resources are not assigned to persistentwireless stations by reading the bitmap (or other signalling), andderiving the location of the free resources.

In some embodiments the method further comprises using a resourceshifting pattern for full persistent resources.

In some embodiments the resource shifting pattern is a cyclic shift.

According to a fourteenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; for at least one OFDM resource, allocatingthe resource as a persistent resource allocation to a group of more thanone wireless stations with only one wireless station being given theresource in a given slot.

In some embodiments the frames are VoIP frames.

In some embodiments the method further comprises transmitting a bitmap(or other signalling) in which each of the wireless stations which havethe same persistent resource have an individual entry, with multiplepositions in the bitmap (or other signalling) referring to the sameresource.

In some embodiments the method further comprises for each persistentresource allocation to a group of more than one wireless stations, eachwireless station of the group of more than one wireless stationsattempting to decode the resource, and discarding a result if it is notfor that wireless station.

In some embodiments the method further comprises: for at least onepersistent resource allocation to a group of more than one wirelessstations, reassigning the persistent resource if it is not assigned toany wireless station of the group of wireless stations to other wirelessstations not receiving a persistent allocation.

In some embodiments for wireless stations being reassigned persistentresources, the resource location is derived from the bitmap (or othersignalling).

In some embodiments the same resource can be persistently allocated tomultiple wireless stations only for a first HARQ transmission.

In some embodiments the same resource is persistently allocated tomultiple wireless stations for multiple HARQ transmissions.

According to a fifteenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; signalling resource allocation to multiplegroups of wireless stations using multiple bitmaps (or othersignalling); re-assigning unused resources available for at least one ofthe bitmap (or other signalling)s to another of the bitmaps (or othersignalling).

In some embodiments the frames are VoIP frames.

In some embodiments the method further comprises wireless stations thatare receiving such unused resources reading their own bitmap (or othersignalling) and the bitmap (or other signalling) of others to determinewhere their resources are.

In some embodiments the method further comprises: starting resourceallocation with the bitmap (or other signalling) associated withwireless stations with the worse channel conditions, and then insequence according to channel conditions until concluding with theallocation for the bitmap (or other signalling) associated with receiveswith the best channel conditions.

In some embodiments the method further comprises performing resourceallocation of a next bitmap (or other signalling) beginning with unusedresources of the previous bitmap (or other signalling).

In some embodiments only those wireless stations not receivingpersistent allocation are repacked into unused resources of anotherbitmap (or other signalling).

In some embodiments the method further comprises: for some wirelessstations, allocating resources that are repacked from resourcesavailable to be assigned by bitmap (or other signalling) of thosewireless stations, and making available unused resources for assignmentto non-persistent wireless stations that are not part of the bitmap (orother signalling) signalled by some other method.

In some embodiments the method further comprises: allocating a firstwireless station to a resource from which a subset is removed due to itshaving been assigned to other wireless stations by a bitmap (or othersignalling) signalling; the first wireless station deriving whichresources are already assigned to other wireless stations from knowledgeof the first resource allocation and the bitmap (or other signalling)that signals the subset to be removed.

In some embodiments the method further comprises: signalling to thefirst wireless station to indicate whether or not the wireless stationmust also read the bitmap(s) (or other signalling) signalling intendedfor other wireless stations, in order to derive which resources havealready been assigned to other wireless stations.

In some embodiments signalling comprises sending a single bit toindicate either 1) the wireless station is allocated all resourcesspecified excluding those allocated to other wireless stations or 2) thebitmap (or other signalling) does not need to be read as all resourcesspecified are assigned to the wireless station.

According to a sixteenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; performing persistent and/or non persistentOFDM resource allocation to multiple wireless stations; capping amaximum transmit power to a given wireless station at a level related tothe longer term channel conditions.

In some embodiments the frames are VoIP frames.

In some embodiments capping a maximum transmit power to a given wirelessstation at a level related to the longer term channel conditionscomprises capping the maximum transmit power according to an inverserelationship to average signal to noise ratio or geometry (path loss andshadowing conditions), of the wireless station.

In some embodiments capping the maximum transmit power according to aninverse relationship to average signal to noise ratio or geometry (pathloss and shadowing conditions), of the wireless station comprisessetting the maximum transmit power to a wireless station during powercontrol operation to a fixed value above the inverse of geometry of thewireless station.

According to a seventeenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; sending a first bitmap (or othersignalling) to indicate which wireless stations are being allocated anOFDM resource during a given scheduling period; sending a second bitmap(or other signalling) to indicate the size of resources and/or MCS's ofwireless stations assigned by the first bitmap (or other signalling).

In some embodiments the frames are VoIP frames.

In some embodiments the second bitmap (or other signalling) contains anentry for each wireless station that is actively being assigned by thefirst bitmap (or other signalling).

In some embodiments each entry is a single bit that indicates small orlarge resource assignment.

In some embodiments the second bitmap (or other signalling) containsentries for persistently assigned wireless stations, regardless ofwhether or not they are assigned, the method further comprising otherwireless stations deriving their resource allocations taking intoaccount the second bitmap (or other signalling).

In some embodiments the second bitmap (or other signalling) does notcontain entries for persistently assigned wireless stations.

According to an eighteenth aspect of the invention, there is provided amethod comprising: transmitting frames using OFDM, each frame occupyinga plurality of OFDM symbols; transmitting a respective bitmap (or othersignalling) for each of a plurality of HARQ interlaces.

In some embodiments the frames are VoIP frames.

In some embodiments the method further comprises: for at least somewireless station, assigning multiple positions in one or more bitmaps(or other signalling) in one or more user groups, a user groupcomprising a set of wireless stations having the same start position ofthe first HARQ transmission of a sub-packet for a given interlace.

In some embodiments the comprises for at least some wireless stations:assigning wireless stations to a bitmap (or other signalling), andpossibly a user group, for a primary assignment, and another position onanother or the same bitmap (or other signalling), in another or the sameuser group, for the purpose of a secondary assignment.

In some embodiments the first transmission is persistently assigned foreither the primary or secondary assignments, or both.

In some embodiments the secondary assignment may be shared by more thanone wireless station while the primary assignment is unique.

In some embodiments start slots and interlaces may be different for theprimary and secondary interlaces.

In some embodiments, a packet that begins transmission for the primaryassignment continues all re-transmissions using the allocations for theprimary assignment; a packet that begins transmission for the secondaryassignment continues all re-transmissions using the secondaryassignment.

In some embodiments the method further comprises: starting transmissionof a packet using the primary assignment and switching to the secondaryassignment after some number of re-transmissions.

In some embodiments the method further comprises persistently assigningresources to the first transmission of the primary and secondaryassignments, where the first transmissions of the secondary assignmentis not allowed to be the first transmission of the packet.

In some embodiments resources are persistently assigned to the firsttransmission of the primary assignment but not the secondaryassignments.

In some embodiments, some user groups of a given bitmap (or othersignalling) refer to wireless stations with start positions of the firstHARQ transmission of a sub-packet in a given slot, and may bepersistently assigned, while other user groups in the same bitmap (orother signalling) may not be persistently assigned.

In some embodiments the presence of a secondary first slot persistentassignment requires the wireless station to monitor the secondarychannel.

In some embodiments the secondary assignment is only used when neededdue to re-transmissions being exhausted on the primary assignment.

According to a nineteenth aspect of the invention, there is provided amethod comprising: assigning a non-shared OFDM transmission resource toa wireless station; assigning a shared OFDM transmission resource to awireless station with information from a shared resource allocationscheme.

In some embodiments assigning a non-shared OFDM transmission resourcecomprises assigning a non-shared OFDM transmission resource usingunicast signalling messages.

In some embodiments assigning shared resources with information from ashared resource allocation scheme comprises assigning shared resourcesusing a bitmap.

In some embodiments assigning a shared OFDM transmission resourcecomprises assigning shared resources of which at least a portion of areunused resources.

In some embodiments the method further comprises assigning unusedresources to one of: a wireless station notified of assignment of theunused resources by a signalling scheme; a wireless terminal that isdesignated to use the unused resources of a shared resource orresources; one or more wireless stations designated to use unusedportions of one or more shared resources.

In some embodiments other resources in addition to the unused resourcesare assigned to the wireless terminal

In some embodiments, if a portion of a transmission sent within theshared resource is not received and decoded by an intended wirelessstation, reception of the packet can proceed without it.

According to a twentieth aspect of the invention, there is provided amethod comprising: assigning a shared OFDM transmission resource to awireless station with information from one of a unicast signallingmethod or a part of the grouped resource allocation scheme.

According to a twenty-first aspect of the invention, there is provided amethod comprising: indicating an assignment of resources with anassignment message; assigning resources from the assignment of resourcesindicated in the assignment message to individual users with a resourceusage bitmap.

In some embodiments the assignment message and the resource usage bitmapare sent either separately or in a single bitmap.

In some embodiments when assigning resources, the resource usage bitmapindicates which resources are available for all resources or a subset ofthe resources.

In some embodiments indicating an assignment of resources comprisesutilizing an assignment bitmap that contains entries corresponding to awireless station or group of wireless stations.

In some embodiments indicating an assignment of resources comprisesutilizing the assignment bitmap to indicate the wireless stations forwhich a transmission is to start.

In some embodiments the method further comprises: for the wirelessstations for which a transmission is to start: determining wirelessstation resource locations from the resource usage bitmap andassignments to other wireless stations.

In some embodiments a wireless station is assigned to only one usergroup so that the wireless station is assigned one position, in a singleassignment bitmap.

In some embodiments if a number of sub-packet transmissions transmittedon a assigned resource is greater then the number of first sub-packettransmission positions, a new packet transmission is started on adifferent resource prior to an earlier packet completing all sub-packettransmissions.

In some embodiments if a wireless station is transmitted multiplepackets in the same interlace offset, the multiple packets aredistributed across composite time slots of the interlace offset.

In some embodiments the method further comprises sending the assignmentbitmap for user groups on different interlaces or interlace offsets.

In some embodiments the method further comprises subdividing a usergroup into more than one user group.

In some embodiments when indicating an assignment of resources,utilizing separate assignment messages for each user group.

In some embodiments the method further comprises transmitting one ormore assignment messages along with one or more resource usage bitmaps.

In some embodiments indicating an assignment of resources comprises: ina given slot, one or more assignment bitmaps are used to indicateassigned users, and a single resource usage bitmap is used to indicateavailable resources based on all current assignments from bitmaps.

In some embodiments when indicating an assignment of resources, theresource usage bitmap comprises entries for a subset of resources or hasentries for all resources.

In some embodiments resources are used for transmission of one or moreof: broadcast, assignment, and control channel messages.

According to a twenty-second aspect of the invention, there is provideda method comprising: for when the maximum number of allowed HARQtransmissions for a packet is not an integer multiple of the number ofinterlace offsets: a wireless terminal recovering from possible feedbackerrors when a negative acknowledgement (NAK) is mistakenly received by abase station for a positive acknowledgement (ACK) or when an ACK ismistakenly received by a base station for a NAK.

In some embodiments the wireless terminal recovering from possiblefeedback errors comprises: when more HARQ transmissions are receivedthan are allowed for an undecoded packet, the wireless station emptyinga buffer storing previously received HARQ transmissions for theundecoded packet and using the most recently received HARQ transmissionas a HARQ transmission for a new packet.

In some embodiments the allowed HARQ transmissions for a packet is fiveand the number of interlace offsets is three.

According to a twenty-third aspect of the invention, there is provided amethod for transmitting a packet comprising: transmitting frames usingOFDM, each frame occupying a plurality of OFDM symbols; allocating afirst OFDM resource within a frame to an original sub-packettransmission for the packet; transmitting the original sub-packettransmission using a modulation and coding scheme; in response toreception information received from a receiver, allocating a secondresource space to send a retransmission sub-packet for the packet, saidsecond resource space being different from said first resource space;and transmitting said retransmission sub-packet using said modulationand coding scheme.

In some embodiments the step of allocating a second resource spacefurther includes allocating a second resource space using said receptioninformation.

In some embodiments the method further comprises: signalling arespective user ID for each retransmission.

In some embodiments the method further comprises: transmitting anACK-NAK-echo bitmap to indicate which wireless stations are receivingallocations for retransmissions.

In some embodiments the method further comprises: transmitting originalsub-packets and retransmission sub-packets with a constant framespacing.

According to a twenty-fourth aspect of the invention, there is provideda system for transmitting a packet comprising: radio circuitry; and acontroller operable to: allocate a first resource space for transmittinga first sub-packet for the packet; provision said sub-packet fortransmission by said radio circuitry using a modulation and codingscheme; in response to reception information received from a receiver,allocate a second resource space to said data packet, said secondresource space being different from said first resource space; andprovision said a second sub-packet for the packet for transmission bysaid radio circuitry using said modulation and coding scheme.

In some embodiments the controller is further operable to allocate asecond resource space using said reception information.

According to a twenty-fifth aspect of the invention, there is provided abase station comprising: a scheduler to schedule packets fortransmission; a signalling information generator to generate signallinginformation based on information received from the scheduler; a framegenerator to construct frames based on information from the scheduler; atransmitter to transmit the frames; a receiver to receive feedback toaid in determining whether the transmitted frames were successfullyreceived.

In some embodiments the scheduler receives the feedback from thereceiver and utilizes the feedback to schedule packets.

In some embodiments the scheduler has access to the packets eitherthrough a physical connection or access to stored memory.

In some embodiments frames generated by the frame generator includesignalling information from the signalling information generator.

According to a twenty-sixth aspect of the invention, there is provided awireless station comprising: a receiver to receiver frames; a signallinginformation decoder to extract signalling channels from received frameand determine whether a resource has been scheduled for the wirelessterminal, and if so where; a sub-packet extraction module to extractsignalling channels from the received frames; a packet decoder to decodeinformation on the signalling channels; a transmitter to sent feedbackindicating whether the transmitted frames were successfully decoded.

In some embodiments when multiple sub-packets for a given packet havebeen received, the multiple sub-packets are used in combination by thepacket decoder to decode the information on the signalling channels.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the attached drawings in which:

FIGS. 1 to 3 are schematic diagrams of VoIP framing methods provided byembodiments of the invention;

FIG. 4 is a block diagram of a cellular communication system;

FIG. 5 is a block diagram of an example base station that might be usedto implement some embodiments of the present invention;

FIG. 6 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present invention;

FIG. 7 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present invention;

FIG. 8 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present invention;

FIGS. 9 to 18 relate to methods of signalling resource assignment;

FIGS. 19 through 21 relate to resource assignment in which primary andsecondary assignments are employed;

FIG. 22 shows an example of a bitmap containing a respective bitposition for each of 10 wireless stations;

FIG. 23 contains an example of a downlink VoIP IE (information element)Format;

FIG. 24 shows an example of overhead estimations for a particularimplementation in which the above described fully dynamic schedulingmechanism is employed compared to an implementation in which a hybrid(static plus dynamic) scheduling mechanism is employed, and alsocompared to the overhead for current 802.16e implementations;

FIG. 25 contains an example of a usage scenario employing a hybrid H-ARQscheme provided by an embodiment of the invention;

FIG. 26 contains an example of a usage scenario employing a hybrid H-ARQscheme provided by an embodiment of the invention;

FIGS. 27A and 27B contain a table comparing the overhead of a fullysynchronous approach, a fully asynchronous approach, and two differenthybrid approaches;

FIG. 28 is a block diagram of an example of a base station that performsscheduling for downlink transmissions;

FIG. 29 is a block diagram of an example of a wireless station thatreceives scheduled downlink transmissions; and

FIG. 30 is a schematic diagram of a portion of a VoIP frame illustratingan example of how a wireless station can recover from a mistakenlydetected NAK (negative acknowledgement) when an ACK (acknowledgement)was sent.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In accordance with embodiments of the invention various HARQ techniquesare described. Specifically the embodiments presented below are intendedfor use in future 3GPP, 3GPP2 and IEEE 802.16 based wireless standards.The broader inventions set out in the summary, however, are not limitedin this regard and are applicable to any futures wireless accessstandards if H-ARQ is supported.

In OFDMA, there is a transmission resource consisting of a set ofsub-carriers in frequency over OFDM symbol durations in time. One ormore, typically consecutive, OFDM symbols constitutes a frame. Framesmay be further subdivided to form slots. A particularly suitable frameduration for VoIP is 20 ms. Having assigned OFDM symbols to framesand/or slots, channelization involves assigning respective subsets ofthe resource to respective channels. There are many ways thatchannelization can be performed. The resources of a given channel mayinvolve contiguous and/or non-contiguous groups of sub-carriers. For thepurpose of this application, any type of channelization may be used.Scheduling involves assigning the channelized resource to particularusers, and performing any signalling necessary for users to know whenand where their resources are being scheduled. In many cases schedulingalso involves reserving future capacity to perform re-transmissions thatmay, for example, occur according to a HARQ protocol. There is anoriginal packet requiring transmission. This is transmitted in a firstsub-packet. Subsequent retransmission sub-packets are sent as necessary.Any retransmission scheme is contemplated. These may include some or allof the first sub-packet and/or additional redundancy to name a fewexamples.

Some embodiments do not employ a slot structure, but rather simplyallocate resources within a frame to multiple users.

Many of the embodiments described herein refer to the use of bitmaps. Abitmap contains a respective bit for each of a plurality of users/groupsof users that is used to signal that user/group of users is beingscheduled. This is a specific particularly efficient example of ascheduling indicator from which users can tell whether or not they arescheduled. Another example would be to explicitly signal user IDs forthe scheduled users. It is to be understood that throughout thisspecification, wherever a bitmap is used, the bitmap or other signallingcan be employed.

Many of the embodiments described herein make use of an ACK-NAK-echobitmap. This is a bitmap that is used to echo the ACKs and/or NAKsreceived by a transmitter from the various receivers in respect ofprevious transmissions. The ACK-NAK-echo bitmap may contain a bit forall users, or only those scheduled. For example, the bitmap mightinclude a “1” to echo an ACK, and a “0” to echo a NAK. The ACK-NAK-echobitmap is a particular mechanism of ACK/NAK echo. More generally, anyACK/NAK echo can be employed with this and other embodiments describedherein. This includes ACK/NAK echoes intended for either a subset or allusers in the system, as well as ACK/NAK echoes intended for a singleuser. The ACK-NAK-echo bitmap indicates whether another sub-packet isbeen transmitted in respect of a given packet. If a previous packet hasbeen acknowledged, the “ACK” indicator indicates that theacknowledgement has been received by the base station (BS), and theretransmission resource will not be used. If a NAK has been received inrespect of a previous packet, then the “NAK” indicator indicates thatthe negative acknowledgement has been received by the BS, and the nextretransmission resource will be used to transmit a retransmissionsub-packet for the packet.

In some embodiments, the ACK-NAK-echo bitmap is transmitted by the BTSto a group of the receivers, and contains a respective bit (or otherindicator) that echoes the ACK or NAK sent by each wireless station inthe group for each VoIP frame. The user group can consist of one user, asubset of all users, or all users in the system. The ACK-NAK-echo bitmapis sent as often as every slot. However, the bitmap may include aposition for a given user only during a subset of the slots. Thus, if awireless station successfully decodes a packet on the basis of one ormore sub-packets received, the wireless station transmits an ACK, andthis shows up in the subsequent ACK-NAK-echo bitmap transmitted by theBS. Similarly, if a wireless station fails to successfully decode apacket on the basis one or more sub-packets received, the wirelessstation transmits an NAK, and this shows up in the subsequentACK-NAK-echo bitmap transmitted by the BS. One of the purposes of theACK-NAK-echo bitmap is to allow all wireless stations to follow alongwith the ACK/NAK status of all wireless stations.

While a wireless station will not know what to expect in theACK-NAK-echo bitmap as a whole, the wireless station will expect to seean echo of its own ACK/NAK. In some embodiments, the base stationtransmits an ACK to echo a NAK transmitted by the wireless station, ortransmits a NAK to echo an ACK transmitted by the wireless station forthe purpose of signalling something to the wireless station. Severalspecific examples of this are presented in the detailed embodimentsdescribed below.

The detailed description of the embodiments in this application for themost part reflects the implementation of embodiments of the invention ona downlink from a base station to wireless stations. More generally,uplink and downlink implementations are contemplated. An allocation of aresource to a wireless station can involve allocation of an uplinkresource for transmission by the wireless station or the allocation of adownlink resource for transmission to the wireless station.

Furthermore, many of the embodiments described herein are applied toVoIP traffic, but may also find application to non-VoIP traffic or tocombinations of VoIP and non-VoIP traffic. Some embodiments that areparticularly suitable for VoIP traffic may also be particularly suitablefor traffic that has similar characteristics to VoIP traffic, such assome video telephony.

In general, the embodiments described herein may be applicable to bothunicast and multicast schemes.

Signalling Bit Suppression for VoIP Allocation

A first embodiment is particularly appropriate for VoIP traffic due tothe deterministic inter-arrival time of VoIP traffic. However, othertraffic that also has a deterministic inter-arrival time may alsobenefit from this approach.

Base stations that are transmitting VoIP packets to VoIP capablewireless stations (hereafter VoIP wireless stations, although they mayhave other capabilities as well) will receive traffic from the networkfor downlink transmission on a roughly periodic basis, for example every20 ms, for each wireless station. The arrival time of packets arrivingfrom the network for multiple wireless stations will typically be moreor less random. In some embodiments, wireless stations with roughly thesame arriving time are grouped and identified collectively by aGroup_ID. Connections are set up one by one, and each time theconnection is set up, it is assigned to one of the groups according toarrival time. This is but one example of a mechanism of forming groups.Other mechanisms of forming groups are described below.

For each scheduling period, a respective bitmap is transmitted for eachgroup. Each wireless station in a group may be associated with acorresponding position in the group bitmap. If a resource is allocatedto a wireless station in a group, the corresponding position for thewireless station in the bitmap may be set accordingly, for example to“1” to indicate allocation, and a “0” to indicate no allocation. FIG. 22shows an example of such a bitmap containing a respective bit positionfor each of 10 users.

For each position in the group bitmap for which resources are to beallocated, corresponding resource allocation parameters are transmitted.Examples of such resource allocation parameters are given below. It isnot necessary to transmit resource allocation parameters for users thatare not allocated in a given bitmap.

Due to the delay limitation of VoIP traffic, multi-user diversity gainis limited, and there would likely be only a very low possibility of useof high end MCS sets. In some embodiments, a reduced set of MCS sets isallowed for VoIP traffic. This might for example be a subset of DIUC(Downlink Interval Usage Code) and repetition combinations, these beinga particular example of MCS sets. For example, in a particularembodiment, only 8 MCS levels are used, and these can be signalled using3 bits as part of the resource allocation parameters.

In some embodiments, a MIMO transmission scheme that may or may notprovide diversity, such as STTD (space time transmit diversity—a MIMOtransmission scheme that that does provide diversity) or BLAST (a MIMOtransmission scheme that does not provide diversity) may be used. Thiscan be signalled on a per resource allocation basis. For example, in animplementation in which the options are only non-MIMO and STTD, a singleMIMO enable bit might be used to indicate whether MIMO is being employedor not for a given resource allocation. If more MIMO modes areavailable, additional signalling bits might be used. This is anotherexample of a resource allocation parameter.

The resource allocated by a given resource allocation will occupy aresource including certain sub-carriers and OFDM symbol durations. Insome embodiments, a limited number of valid packet sizes for VoIPtraffic are employed (for example, 1, 2 or four) and the size issignalled as part of the resource allocation parameters. The amount oftime/frequency OFDM resource occupied by a VoIP packet can then bederived from the MCS and the size.

For example, if the packet is 40 bytes in size, and an MCS with QPSKwith ½ coding rate is being used, then the 40 information bytes become40×8 bits=320 information bits. After coding, this becomes 640 codedbits. After QPSK, this becomes 320 symbols. Each symbol maps to onesub-carrier. Assuming each sub-channel includes 80 sub-carriers. Asub-packet for this particular packet will occupy four sub-channels.

Allocations may be one dimensional, meaning a single parameter canindicate the size of the allocation. A specific example of a onedimensional allocation is a number of sub-channels. Note that asub-channel may occupy multiple sub-carrier locations on one or multipleOFDM symbols. Allocations may be two dimensional, meaning that twoparameters are used to indicate the size of the allocation. A specificexample of a two dimensional allocation is a number of sub-channels oversome number of scheduling intervals, such as slots. Typically, only aone dimensional allocation is used for a given VoIP user. In someembodiments, where a one dimensional OFDM resource allocation scheme isused (for example allocation is a number of sub-channels), the size ofthe one dimensional OFDM resource allocation can be derived from the MCSand packet size. A specific example of this was presented above.

Due to the low arrival data rate of VoIP traffic, a small number of ARQchannels may be implemented. For example, in some embodiments 4 ARQchannels are implemented each of which can be identified with a 2 bitACID (ARQ channel identifier). The particular ARQ channel assigned for agiven sub-packet may be signalled as part of the resource allocationparameters.

For the particular examples detailed above, a total of 8 bits can beused to signal each allocation signalling namely:

-   -   3 bits MCS;    -   2 bits sub-packet size;    -   2 bits ACID (only needed when there is fully asynchronous HARQ);    -   1 bit MIMO mode.

Therefore, the overall signalling scheme for this example includes thegroup bitmaps and the resource allocation parameters for each groupbitmap. The particular parameters included are implementation specific,and of course, the manner of signalling is also implementation specific.The particular order used for this signalling does not matter so long asit is known at both the transmitter and the receiver. For example, insome implementations, each group bitmap is followed immediately by theresource allocation parameters. Alternatively, all of the bitmaps can besent, followed by the resource allocation parameters for all of thebitmaps.

For this embodiment, HARQ retransmissions are signalled in the samemanner as original transmissions if a fully asynchronous approach isfollowed. For synchronous HARQ, the retransmissions do not need to besignalled.

In accordance with another embodiment of the invention a scheme forallocating resources, to begin, wireless stations with roughly the samearrival time as described above, and/or similar channel conditions,and/or same or similar MCS, may be grouped and identified by a Group_ID.Once again, a respective bitmap is transmitted for each group, and eachwireless station in a group is associated with a respective position ofthe group member bitmap as in the above example. In some embodiments,one or more groups are used for VoIP users, and one or more groups arefor non-VoIP users.

For each user that is being allocated resources, resource allocationparameters are transmitted. In some implementations, two different setsof MCS level signalling are used, a first set for VoIP users, and asecond set for non-VoIP users. For example, MCS level signalling may be4 bits for non-VoIP users allowing for a selection between 16 differentMCS levels, and some other number of bits as low as 0 bits for VoIPusers.

For non-VoIP users, the duration (size of resource region—which could bea one or two dimensional resource) and location may be derived from asignalled indication of a start point of resource allocation for a givengroup (for example 6 bits) in combination with a signalled allocationsize (for example 6 bits) and/or sub-packet size and MCS (for example 4bits).

For VoIP users, the duration and location may be provided as describedabove or derived from a signalled indication of a start point ofresource allocation for a given group (for example 6 bits), and anindication of the assigned resources to a subset of the users (frombitmap); knowledge of at least one of MCS and channel size which may beavailable in some other manner, constant, limited to a searchable set,or implied by membership in a particular group.

Therefore, the overall signalling scheme for this example includes thegroup bitmaps and the resource allocation parameters for each groupbitmap. The particular order used for this signalling does not matter solong as it is known at both the transmitter and the receiver. Forexample, in some implementations, each group bitmap is followedimmediately by the resource allocation parameters. Alternatively, all ofthe bitmaps can be sent, followed by the resource allocation parametersfor all of the bitmaps.

For this embodiment, HARQ retransmissions are signalled in the samemanner as original transmissions assuming an asynchronous HARQimplementation.

For synchronous HARQ, the retransmissions do not need to be signalled.This approach may result in less signalling for re-transmissions, if thesame resource size is to be used for re-transmissions is used as fororiginal transmission.

The following is a specific example of a synchronous HARQ embodiment. Tobegin, wireless stations with roughly same arriving time, and/or similarchannel conditions, and/or same or similar MCS, may be grouped andidentified by Group_ID. Each wireless station in a group may beassociated with a respective position of the group member bitmap as inprevious examples.

In this embodiment, a second bitmap with a respective entry for eachuser assigned resources by the first bitmap is used to indicate if thetransmission is a first sub-packet for a new sub-packet or are-transmission sub-packet. In a particular example, if the resource isassigned for first sub-packet transmission to a given wireless station,the corresponding position for the wireless station in the second bitmapmay be set to ‘1’ whereas if the resource is assigned for aretransmission sub-packet, the corresponding position for the wirelessstation in the second bitmap may be set to ‘0’. The position in thesecond bitmap can be derived from relative position and resourceassignment indications in Group_ID bitmap.

For a first sub-packet transmission, the complete set of resourceallocation parameters (whatever they may be for a given implementation)are signalled.

MCS level signalling may vary by group. For example, it may be 4 bitsfor non-VoIP, and as low as 0 for VoIP users. Duration (size of resourceregion—could be one or two dimensional resource) and location may bederived from indication of start point of resources (6 bits) forGroup_ID, allocation size (6 bits) and MCS (4 bits) for listed usersthat are assigned resources. For VoIP, resource allocation may beprovided the same as described above or derived from an indication ofthe assigned resources to a subset of the users (from bitmap), andknowledge of at least one of MCS and channel size which may be availablein some other manner, which may be constant, limited to a searchableset, or implied by membership in Group_ID.

For HARQ re-transmission assignments, the MCS and resource location neednot be signalled as the resource size may remain unchanged and thelocation can be derived from at least a portion of the 2 bitmaps andknowledge of resource size or MCS from initial signalling. In someembodiments, the bit field sizes may change for re-transmissiondepending on application specifications in which case the sizes wouldneed to be signalled.

In some embodiments, HARQ re-transmission assignments are not performedfor certain users, for example for VoIP users, where it is known thatthe re-transmissions for these users will use the same resource as theoriginal resource, or another known resource.

Scheduling Mechanism

In some embodiments, using one or more of the above resource allocationapproaches, a fully dynamic resource allocation is employed meaning thata completely new allocation is performed for each scheduling interval.This can be based on real time CQI (channel quality indicator) fed backfrom individual receivers in combination with a delay bound that mightexist, particularly for VoIP traffic.

In some embodiments, a hybrid (static and dynamic) allocation isemployed. For this embodiment, a resource allocation can be determinedand held constant for some period (for example N frames, N>1) based forexample on estimated arriving data rate and average CQI. Such a staticallocation may be used for first sub-packet transmissions. Dynamicresource allocation may be employed for additional resource allocation(e.g., for retransmissions).

In accordance with an embodiment of the invention FIG. 23 provides anexample of a downlink VoIP IE (information element) Format. The fieldsinclude an extended-2 DIUC that is used to indicate the type of IE. Moregenerally, there may be any message type indicator) in which differentDIUC are used to differentiate MIMO or non-MIMO; length; VoIP_Group_IDidentifying to which group of users this IE pertains; atraffic_indication bitmap containing a bit for each user in the group.Then, for each “1” in the bitmap, there are further fields that includea sub-packet size field, a VoIP_DIUC field that is used to signal MCS,ACID, and AI_SN (assignment indication sequence number) used to indicatewhether a sub-packet is an original sub-packet or a re-transmissionsub-packet.

FIG. 24 shows an example of overhead estimations in numbers ofsubchannel used for transmission of overhead for a particularimplementation in which the above described fully dynamic schedulingmechanism is employed compared to an implementation in which the abovedescribed hybrid (static plus dynamic) scheduling mechanism is employed,and also compared to the overhead for current 802.16e implementations.The comparison is made for differing numbers of allocations, namely 8,16, 32, this being how many VoIP users are supported in each frame. Itcan be seen that there is approximately a 50% to 60% overhead reductionfor the fully dynamic allocation scheme, and a 60% to 70% overheadreduction for the hybrid scheme.

More generally, grouping of users into groups can be done according toany appropriate mechanism. In another example, users are grouped intogroups for which a common control channel will be transmitted, forexample a DCCH (dedicated control channel). Such a group can be referredto as a DCCH group. In some embodiments, this grouping is based ongeometry. For example, cell coverage might be divided into three roughlyannular regions each with a respective DCCH group. The uses in each ofthe annular region re-assigned to the respective DCCH group. A firstDCCH is transmitted for reception by users in the innermost area withlowest MCS, a second DCCH is transmitted for reception by users in themiddle area, and a third DCCH is transmitted for users in the outermostarea with the highest MCS. In another embodiment, grouping into DCCHgroups is performed based on channel quality.

For example, there might be 30 users within the coverage area of a BTS.Of these, users 1-10 that are closest to the BTS and/or have the bestchannel and might be put together in a first group and signalled to witha first signalling channel, e.g. DCCH-0. Users 11-20 that are nextclosest and/or have the next best channel and are grouped into a secondgroup and signalled to with a second signalling channel, e.g. DCCH-1.Users 21-30 that are farthest away and/or have the worst channel and aregrouped together in a third group and signalled to with a thirdsignalling channel, e.g. DCCH-2. These signalling channels can come inany appropriate form. Note that within each of the group, furthersub-division into groups based on arrival time as described previouslycan be performed. The signalling channels may be broadcast channels inwhich case all users need to be able to receive them. If only a singlesuch channel is used, then all users in the whole cell need to be ableto receive it. By dividing users as described above and using multiplesignalling channels, less robustness on the signalling channel for userswith good channels can be employed.

Signalling to indicate whether or not a given user is being allocatedresources is done again using a bitmap. The position in the bitmap maybe assigned when the user joins. For example, the bitmap may signal ‘1’if the user is scheduled, ‘0’ otherwise. Users assignment to groups maybe semi-static (intended to be long-term). In some embodiments, thebitmap length can be changed slowly. Each user knows whether or not itis scheduled from the bitmap. Each user that is scheduled reads theassociated resource allocation parameters. In some embodiments, theseinclude an MCS and resource size.

In some embodiments, a persistent assignment is used for firstsub-packet transmissions to a given user, meaning that the assignmentdoes not change from one scheduling period to the next, while HARQretransmission sub-packet is transmitted on a OFDMA time/frequencyresource than is different from the original persistent assignment. Insome embodiments, a HARQ ACK-NAK-echo bitmap is introduced to re-packthe resource assigned to HARQ retransmissions, such that the left-overresource for other users are contiguous in a slot. This reduces thesignalling overhead required to assign resources to other users. Aspecific example of this is described below.

In some embodiments an MCS scheme for transmissions remains the same fororiginal transmissions and retransmission, and is signalled once for thefirst transmission. The resource allocation locations for retransmissionmay be flexibly assigned in locations that need not be the same as thatfor the first transmission.

This technique allows for a less complex scheduler and a reduction insignalling overhead as compared to fully asynchronous and fullysynchronous approaches. In a fully asynchronous approach, signalling isemployed for first and subsequent sub-packet transmissions, anddifferent spacing and/or physical resource locations can be employed. Ina fully synchronous approach, the spacing between sub-packettransmissions is fixed, and the same physical resource is used.

In some embodiments, user IDs are used to signal that retransmissions tospecific users are being performed. Signalling may include only user IDswith other signalling parameters being the same as signalled previouslyfor the original transmission.

In some embodiments, an ACK-NAK-echo bitmap is used for retransmissions.Signalling may include ACK-NAK-echo bitmap (DL).

Using the user ID approach, the signalling overhead may be less thanthat of full asynchronous scheme by about 25-30% while the signallingoverhead is comparable or more than that of fully synchronous scheme byabout 10%. Flexibility, however, is achieved as compared to the fullysynchronous scheme because the resource allocation location may vary forretransmission using the hybrid H-ARQ technique.

Using the ACK-NAK-echo bitmap approach, the signalling overhead may beless than that of the fully asynchronous scheme by 32-46%. Using thesecond approach, the signalling overhead may be comparable to or evenless than that of the fully synchronous scheme by 16-21%, and thescheduler complexity caused by the fully synchronous H-ARQ scheme may beavoided.

According to another embodiment of the invention sub-packettransmissions including the original and re-transmission sub-packetshappen with a regular N slot spacing, N being some defined parameter.That is to say if the first transmission happens in slot i, the secondtransmission is performed in slot i+N, the third transmission in framei+2N and so on. According to other embodiments, however, there-transmission interval need not be fixed.

According to an embodiment of the invention, operation of a hybrid H-ARQscheme may be provided by the following:

a) BS allocates resources sequentially. The packets with higher numberof retransmissions are scheduled before the packets with lower number ofre-transmissions;

b) The resources allocated for the K-th transmission are signalled by anInformation Element (IE_Tx-K);

c) IE_TX-1 (for first transmission) format may include the followinginformation:

Start BAU (basic access unit—a minimum unit of resource allocationdefined in any application specific manner) index (more generally astart point into the physical resource allocation);

Number of assignments;

For each assignment:

Number of BAUs (more generally an indication of amount of resourceallocation for each assignment);

User ID;

MCS (modulation and code rate);

d) IE_TX-k (k=2, . . . , maximum number of retransmission, k≠1, forre-transmissions) format may include the following information which isless than above for original transmissions:

Approach 1:

Start BAU index

Number of assignments

For each assignment: User ID

Approach 2:

Start BAU index;

ACK-NAK-echo bitmap (the size equals the number of negativeacknowledgements (e.g.‘0’) in the IE_TX-k−1 in frame N frames before thecurrent frame), assuming that only users that failed a k−1^(st)transmission N frames earlier will require a kth transmission in thecurrent frame. The ACK-NAK-echo bitmap may be created by the BS based onthe H-ARQ feedback from wireless stations regarding the packet decoding.

A wireless station may record the order of assignments and assignmentsizes for each assignment from the IE_TX-k, k=1, . . . , maximum numberof retransmissions. The wireless station may derive its resourceallocation based on the this record.

As will be appreciated by one of ordinary skill in the art othersignalling formats are possible without departing from the broader scopeof the invention (e.g., combination index approaches).

Referring now to FIG. 26, shown is an example of a usage scenarioemploying a hybrid H-ARQ scheme provided by an embodiment of theinvention that follows the second above-identified approach, namely theuser of ACK-NAK-echo bitmap to signal retransmissions. For this example,it is assumed that a maximum of two retransmissions can be performed,but this can be generalized to an arbitrary maximum number. The resourceassigned for first, second (first retransmission) and third (secondretransmission) sub-packet transmissions is indicated at 400,402,404,respectively. The allocation to OFDM sub-carriers is performed accordingto these assignments, but note that it is a logical assignment. Asdescribed for other embodiments, the actual sub-carriers may notnecessarily be contiguous and may belong to multiple OFDM symbols.

During a first frame (frame i) 406, a first set of users, ten in theexample, are scheduled to transmit an original sub-packet. This maypertain to VoIP and/or non-VoIP traffic. To signal this, IE_TX-1 430 issent. Any appropriate signalling mechanism can be employed. In the nextframe (i+1) 408, original sub-packets for users 11 to 20 aretransmitted. To signal this, IE_TX-1 432 is sent. Meanwhile users 1-10provide feedback—illustratively shown as a sequence of bits 418 thatindicate whether a given user successfully decoded their packet, butthis represents a summary of feedback coming from each wireless stationseparately. Feedback 418 indicates that users 2,4,10 did notsuccessfully decode their packets. In the third frame (i+2) 410,retransmissions are scheduled first, followed by first sub-packettransmissions for next group of users 21 to 30. Users 2,4,10 requireretransmission, and as such these are scheduled first. The signallinginformation is IE_TX-2 434 associated with second transmissions, andIE_TX-1 436 for the first transmissions. For the IE_TX-2, anACK-NAK-echo bitmap is used to signal. From this bitmap, the users 1-10understand that the first three resource allocations will be assigned tousers 2,4,10 in sequence. Receivers can look at first resourceassignment to understand the size of the retransmission resource, theassumption being that it will be the same. Meanwhile feedback 420 inrespect of the first sub-packet transmissions to users 11 to 20 isreceived at 420. In the fourth frame (i+3) 412, there areretransmissions for the group of users 11-20 transmitted to during thesecond frame (i+1). In this case, this includes retransmissions forusers 11,12 and 14. Meanwhile, feedback from the second, fourth, andtenth users in respect of the second sub-packet transmissions isreceived as indicated at 422, and this is shown to indicate that thethird such user (namely user 10) signals failure and requiresre-transmission. In the fifth frame (i+4) 414, the allocation beginswith an allocation for the third sub-packet transmission for user 10 andthis is signalled with IE_TX-3 442. Another IE_TX-2 444 is used tosignal second sub-packet transmissions, and another IE_TX-1 446 is usedto signal first sub-packet transmissions. A similar process is shown forthe sixth frame (i+5) 416 with IE_TX-3 448, IE_TX-2 450, and IE_TX-1452. The assumption for this example is that the spacing betweenretransmissions is fixed, but the location within the frame can change.A contiguous resource is available for new assignments.

Referring now to FIG. 25, shown is an example of a usage scenarioemploying a hybrid H-ARQ scheme provided by an embodiment of theinvention that follows the first above-identified approach, namely theuse of user identifiers. This example is basically the same as theexample of FIG. 26 described above except that rather than usingACK-NAK-echo bitmaps to signal retransmissions, user identifiers areused. For example, a 16 bit ID per user might be employed.

For the examples of FIGS. 25 and 26, it is assumed that 70% of packetswill get through after the first sub-packet transmission; 20% getthrough after the second sub-packet transmission; and 10% will getthrough after three sub-packet transmissions. The frame space betweentwo sub-packet transmissions for a given packet is assumed to be twoframes for this example.

FIGS. 27A and 27B contains a table comparing the overhead of a fullysynchronized approach, a fully asynchronous approach, and two differenthybrid approaches. For the comparison, the following assumptions aremade:

Number of BAUs: 128; total 50 transmissions (first andre-transmissions); Size of user ID: 10 bits; Size of MCS: 3;

30% more signalling overhead for fully synchronous scheme to account forthe impact of irregular vacancies of the resource available to assign tothe first transmission.

For a first scenario, represented in the top half of the table of FIGS.27A and 27B, it is assumed that for successful decoding, 70% of packetsrequire one transmission; 20% of packets require two transmissions; 10%of packets require three transmissions.

For a second scenario, represented in the bottom half of the table ofFIGS. 27A and 27B, it is assumed that for successful decode, 50% ofpackets require one transmission; 25% of packets require twotransmission; 15% of packets require three transmissions, 8% of packetsrequire four transmissions; 2% of packets require five transmissions.

Handling of Non-Full Rate Vocoder Frames

To reduce signalling overhead for VoIP, persistent resource allocationcan be used to assign periodic resources to VoIP users to transmit aVoIP packet every fixed time interval, e.g. 20 ms, as previouslydescribed above.

In some embodiments, the persistently assigned resource can be used fortransmission of both first sub-packet and subsequent HARQ retransmissionsub-packets. If HARQ early termination occurs meaning that successfulpacket decoding has occurred prior to the use of all of the allocationsfor retransmission for a given packet, the persistent resource can beassigned to other users in a non-persistent manner. In this case, theavailable resource to other users due to HARQ early terminated isfragmented in a slot. Alternatively, as described in other embodimentsabove, a HARQ retransmission sub-packet may be transmitted on adifferent OFDMA time/frequency resource than the original persistentassignment. In some embodiments, a HARQ ACK-NAK-echo bitmap isintroduced to re-pack the resource assigned to HARQ retransmissions,such that the left-over resource for other users are contiguous in aslot. This reduces the signalling overhead required to assign resourcesto other users.

The above-described approaches do not specifically address the unusedresource or fragmentation of a resource that occurs as a result ofvariable rate vocoder frames. Note that a “vocoder frame” is an exampleof what might be transmitted as a packet, not to be confused with theOFDM framing that might be employed in some embodiments. For example, anEVRC codec generates voice frames with four different rates or framesizes: full rate, ½ rate, ¼ rate and ⅛ rate (which is blanked) withprobabilities of 29%, 4%, 7% and 60% respectively. With variable sizevocoder frames, the resource required by the first sub-packet of a VoIPpacket is variable. Therefore, pure persistent resource allocation forthe first sub-packet transmission may not be efficient.

In this embodiment, there is a persistent allocation for the firstsub-packet transmission, but the resource allocation may or may not beused as allocated. Furthermore, mechanisms are provided to increase thelikelihood of a first sub-packet resulting in a successful decodingoperation at the receiver.

Half Rate and Quarter Rate Frame Transmission

For half rate, and quarter rate vocoder frames, the frame size issmaller than that of the full rate frame. However, in some embodiments,to avoid additional signalling for the first sub-packet transmission,the same OFDMA time/frequency resource is used for these reduced rateframes as for the full rate frame.

To match the vocoder frame size to the amount of OFDMA time/frequencyresource, an increased coding rate (compared to the full rate frame)and/or repetition is used for the half rate and quarter rate frames.

The different coding rate and repetition factors used for full rate,half rate, quarter rate vocoder frames are predetermined and known tothe wireless station.

The wireless station may use blind rate detection to detect the actualframe rate transmitted by the base station. Alternatively, this could besignalled, but this would be less efficient.

When a first sub-packet is scheduled, typically resources are madeavailable later on for HARQ retransmission should it be necessary.However, the above-described approach will lead to a higher probabilityof success for first sub-packet transmission of half rate and quarterrate frames. HARQ early termination occurs when a sub-packet issuccessfully received using less than all of the allocatedretransmission resources. The resource freed up by the persistent userdue to HARQ early termination can be assigned to other users. Thisembodiment may employ a persistent allocation for both the originalpacket and retransmissions.

More generally, the above approach can be used for any non-full rateframes. For example, in implementations where ⅛ frames are not blanked,the repetition or increased coding rate approach can be employed.

⅛ Rate Frame Transmission

⅛ rate vocoder frames can be blanked without impacting the vocoderperformance. In some embodiments, rather than transmitting a ⅛ frameduring every persistently allocated opportunity, keep-alive ⅛ rateframes can be sent once in a while, for example in a periodic manner.The method of non-full rate frame transmission as described in theprevious section can be used for the keep-alive, that approach resultingin an increased chance of successful transmission, and accordinglyresulting in retransmission resources being frequently freed up. Duringthe persistent allocations that are not used for transmitting thekeep-alive ⅛ rate frames, non-persistent resources can be assigned.While this aspect has focussed on ⅛ rate frames, more generally, minimumrate frames can be treated in this manner.

When a ⅛ rate VoIP frame is blanked, the persistently allocated resourcefor the first sub-packet does not contain content for the originallyallocated user.

Resource for First Sub-Packet Left Unused

In a first implementation, the resource for the first sub-packet is leftunused meaning that it is not reallocated to another user. In this case,the wireless station having the persistent allocation receives nothingand interprets it as an erased packet. The wireless station signals aNAK to the BS.

The BS will understand that the transmission has been blanked. In thesubsequent retransmission slots, the BS sets the corresponding bit inthe ACK-NAK-echo bitmap to ‘ACK’ to indicate that there is no resourceassigned to this user for HARQ retransmission. More generally, the BSsignals that there will be no retransmission. The unused retransmissionresource is then available to be re-packed and can be assigned to otherusers.

The wireless station with the blanked transmission will either a)discover that its NAK has been changed to ACK and determine it is beingblanked for this frame or b) not receive the ACK-NAK-echo bitmap (forsignal strength reasons, or otherwise) and follow the same procedure asin the first slot.

Resource for First Sub-Packet Assigned to Other Users

In a second implementation, the unused resource is assigned to otherusers in a non-persistent manner. The resource assignment may forexample be identified by specific resource/channel/node index or OFDMAsub-carrier and symbol indices.

In this case, the original persistent user with the blanked transmissionwill unknowingly decode the packet transmitted on its persistentresource space. The decoding will most likely fail, in which case, theuser signals a NAK to the base station. In the case where the usersuccessfully decodes the packet, an ACK will be sent to the basestation. The layer 2 protocol of the user will however detect a mismatchon the user ID and will discard the packet. The base station will ignorethe HARQ ACK/NAK received from the original persistent user.

If the non-persistent user occupying the unused persistent resource doesnot require HARQ retransmission, at the retransmission slot, the BS setsthe corresponding bit in the ACK-NAK-echo bitmap to ‘ACK’ to indicatethat there is no resource assigned to the persistent user for HARQretransmission. The unused resource is therefore re-packed and can beassigned to other users.

On the other hand, if the non-persistent user occupying the unusedpersistent resource requires HARQ retransmission, two differentapproaches are provided to setting the HARQ ACK-NAK-echo bitmap insubsequent retransmission slots:

Approach 1: The retransmission of a sub-packet for the non-persistentuser occupies a different resource than the previous sub-packet. The newresource is explicitly signalled. The BS sets the corresponding bit inthe ACK-NAK-echo bitmap to ‘ACK’ to indicate that there is no resourceassigned to the persistent user for HARQ retransmission. The unusedpersistent resource is therefore re-packed and can be assigned to otherusers.

Approach 2: The retransmission of the sub-packet for the non-persistentuser occupies the same resource as the previous sub-packet. No explicitsignalling is required for the retransmission. The BS sets thecorresponding bit in the ACK-NAK-echo bitmap to ‘NAK’ to indicate thatthere is a resource assigned to the persistent user for retransmission.The original persistent user will continue to attempt to decode thepacket transmitted on the persistent resource, if it does not know itsVoIP packet has previously been blanked.

In some embodiments, a timeout period is defined such that if a user has⅛ rate frames for more than that period, the persistent allocation tothat user is released. In this case, the silence period can be quitelong so the persistent allocation is deassigned, and reassigned later,for example after a timeout limit.

VoIP Packet Jitter Handling

VoIP packets arrive at random intervals due to delay jitter at thewireline networks. Therefore, there is no guarantee that a VoIP packetwill arrive at the layer 2 buffer at every 20 ms boundary, where thepersistent resource is assigned.

In some embodiments, to address this problem, a small ‘de-jitter’ delayis artificially added to every VoIP packet that arrives at the layer 2buffer such that the probability of a packet available at every 20 msboundary is above a predefined threshold. If there is no packet at a 20ms boundary, the transmission on that slot is blanked. The blankedresources are allocated to other users.

Three approaches to deliver a packet that arrives after the 20 msboundary (i.e. late packet) are provided:

Approach 1: Transmit the packet in a lower MCS format intended for areduced number of retransmission trials. The lower MCS format has ahigher likelihood of successful transmission over the reduced number ofretransmission trials. In some embodiments, packets arriving after somenumber of retransmission slots, for example after the secondretransmission slot, maybe delayed to the next 20 ms frame.Approach 2: Delay the packet transmission until the next 20 ms frame. Insome embodiments, delayed and current VoIP packets are combined into acomposite packet. In other embodiments, the delayed and current VoIPpackets are not combined into composite packets.

In some embodiments, persistent allocation is supplemented withadditional non-persistent resources for that 20 ms frame; only oneACK/NAK is required from the wireless station for the composite packet.Separate ACK/NAK echoes can then be used for the persistent andnon-persistent allocation.

In other embodiments, the composite packet is transmitted using assignedpersistent resources by changing the MCS accordingly. This involves thesame persistent allocation: one ACK/NAK from the wireless station, andone ACK/NAK echo. The “missed frame” will trigger blind detection of MCSfor the composite packet in the next frame.

Approach 3: Delay the packet transmission until resources becomeavailable. Packets continue to be sent in sequence without combiningmultiple voice packets into composite packets. As opposed to approach 2,there is no need to supplement the resource allocation withnon-persistent resource. The layer 2 buffer will have a chance to beemptied out during blanked transmission times (i.e. occurrence of ⅛ rateframes).

VoIP Capacity Increasing Schemes

Conventional system frame-synchronize VoIP users to start new packetsevery 20 ms. This leads to an increasing probability of holes later inthe 20 ms frame. This is desirable if there is a lot of non-persistenttraffic to schedule, but this limits VoIP traffic.

In a first approach to improving VoIP capacity, a staggered allocationscheme is provided by an embodiment of the invention. VoIP transmissionto users begins with equal or similar probability in each slot. Overtime, loading per slot will be approximately constant (some user earlyterminate, others start first transmissions). It is possible to allocatesome non-persistent resources to VoIP temporarily in case of resourceemergency. This supports “over-loading” without having to drop or delaypackets. A specific example is illustrated in FIG. 1. Note thatre-transmissions preceding the “1^(st) tx₁ new packet” are in respect ofa previous packet. In FIG. 1, the OFDM resource that is being allocatedis a 20 ms frame. Time is shown in the horizontal direction. In thevertical direction, there is a plurality of sub-carriers, not shown.Each 20 ms frame 300 is divided into slots 302,303,304,305. In theillustrated example, each frame contains four slots. Four different usergroups are defined referred to as User Group 1 306, User Group 2 308,User Group 3 310 and User Group 4 312. The users of the User Group 1 306have their first sub-packet transmissions occurring during the firstslot 302. The users in User Group 2 308 have their first sub-packettransmissions occurring during the second slot 303. The users in UserGroup 3 310 have their first sub-packet transmissions occurring duringthe third slot 304. The users in User Group 4 312 have their firstsub-packet transmissions occurring during the fourth slot 305. There-transmission resources for the users groups other than User Group 1306 will rollover into the frame in a cyclic manner. A firsttransmission and re-transmissions for a given wireless station or groupof wireless stations occur on the same interlace in each respective slotof the frame.

In a second approach to improving VoIP capacity, users are divided intodifferent classes with different numbers of maximum HARQretransmissions. For example, users with more reliable CQI estimates canbe grouped together, and allowed fewer re-transmissions.

In a specific example shown in FIG. 2, two classes are defined, althoughany number N of classes is possible. Then, each VoIP frame is dividedinto multiple sub-frames. This might for example involve dividing 20 msframe into two 10 ms sub-frames (or four 5 ms). In the example of FIG.2, the same frame structure as was described above for FIG. 1 is used. Afirst user class is indicated at 320. A second class of users isindicated at 322, and this includes two sub-groups 324,326. The users inthe first class 320 are allowed an original packet transmission andthree re-transmissions. The users of the second class 322 are allowed anoriginal transmission and a single re-transmission. The sub-frame forthis example consists of the first two slots 302,303 used for user class2, group 1 324 and the second sub-frame consists of the third and fourthslots 304,305 that are used for user class 2, group 2 326. Within any ofthese users groups, the above-discussed approach of distributing thefirst sub-packet transmission across the slots utilized for the classcan also be used.

In some embodiments, a high speed user (more generally a user with alower quality channel) uses a 4-transmission 20 ms frame for increasedreliability.

In some embodiments, a low speed user (more generally a user with abetter quality channel) uses a 2-transmission 10 ms frame as CQIfeedback is more reliable.

In some embodiments, a user does not need to know what class it belongsto. If a packet fails after two transmissions, the user will send a NAK.If this user is intended to have two transmissions, the BS sets thecorresponding bit on the HARQ ACK-NAK-echo to ‘ACK’.

The receiver will then know its resources have been temporarilysuspended for the second half of the frame.

In a third approach to increasing VoIP capacity, for some VoIP users,larger frames are allocated in multiples of 20 ms frames.

In a specific example, for a 40 ms case: one packet is delayed ˜20 msand/or two packets are combined to form composite packet. Compositepackets can have up to eight transmissions, rather than four for a 20 msframe size. A benefit of this implementation is a larger number ofre-transmissions are possible, which is useful for cases when CQIestimates are unreliable. Also, in some embodiments, this implementationprovides improved handling of packet jitter.

A specific example of this is indicated in FIG. 3 for user 1 340. Inthis case, a 40 ms frame 342 has been defined that contains eight slots.The first slot is used for the first transmission for the user 340 andthen there are seven available slots for re-transmission. Each packet isa composite packet formed of two packets for the user. More generally,any number of packets can be combined into a composite packet and anynumber of re-transmissions for the composite packet can be allowed. Ofcourse if too many packets are combined in a composite packet, the delayexperienced by earliest of those packets may become unacceptable.

In an alternative, the transmission of consecutive packets is such thatthe second packet is transmitted immediately (i.e. next slot in the sameHARQ interlace) following the successful reception of the first packet(i.e. ACK returned). The number of re-transmissions for each packet canbe limited. A specific example is shown in FIG. 3 for a user indicatedat 344. For this user, a first packet transmission has taken place inthe first slot and a re-transmission in the second slot. Immediatelyfollowing the re-transmission, which is assumed to be successful forthis case, the second packet is transmitted using the third slot. Up tofour re-transmissions are made available for the re-transmission ofeither the first or second packet in this case. The resources for user 2344 that would have been allocated in the seventh and eighth slots canbe re-allocated to other users.

Implicit Indication of MCS by Unique Mapping of MCS to ResourceAllocation Size

VoIP may use one of several modulation and coding schemes (MCS). In someembodiments, the MCS levels are chosen such that there is a uniquemapping of MCS to physical resource allocation size. Assuming thisunique mapping is known to the receiver, the MCS can be uniquelydetermined by the receiver from the size of the physical resourceassigned to that transmission. The following is a specific example whereone DRCH (dedicated resource channel, an example of a minimum resourceallocation unit) is assumed to be 81 logical tones (i.e. sub-carriersmay or may not be contiguous, may or may not be part of a single OFDMsymbol) and a full rate packet carries 208 bits:

-   -   QPSK, code rate ⅓—4 DRCH (more generally a first resource        allocation size)    -   QPSK, code rate ⅔—2 DRCH (more generally a second resource        allocation size)    -   16 QAM, code rate ⅔—1 DRCH (more generally a second resource        allocation size).        The MCS is determined at the receiver by knowing the number of        DRCH's assigned to this transmission. The allocation size will        be made available to the receiver, through signalling, or some        other manner.

In some embodiments, the resource allocation and modulation schemes donot change for ½, ¼ and ⅛ (when applicable) transmissions so the samemapping applies.

A benefit is that the MCS does not have to be signalled. The uniquemapping of MCS to physical resource allocation size for VoIP thatenables the implicit indication of MCS from the combination index (amethod of control signalling) is described in U.S. Patent ApplicationNo. 60/748,555 filed Dec. 8, 2005 incorporated by reference in itsentirety and in U.S. Patent Application No. 60/792,486 also incorporatedby reference in its entirety.

Specific OFDMA frame sizes, slot sizes, OFDM symbols, coded frame rates,HARQ re-transmission schemes have been described for the purpose ofexample only.

Further Resource Assignment Examples

In some embodiments, during a given slot, a user must be able todetermine if it is being assigned resources for transmission orre-transmission of a VoIP packet. The user needs to be able to determinewhich resources have been assigned to it.

In some embodiments described above, the resources are re-packed toprevent holes within the resource block. However, a user assignedresources still needs to be able to determine where its resources arelocated after each re-packing process (every slot).

In embodiments in which a persistent allocation is used, resources arein a fixed location for a user's first transmission. A user will knowexactly where its resources are for the first HARQ transmission of apacket which is beneficial as it does not require signalling. Re-packingshould not affect this resource assignment for first HARQ sub-packettransmission, and all users will need to be able to understand there-packing mechanism when persistent allocation is used.

Bitmap

In some embodiments, a user bitmap is employed. The user bitmapindicates if resources have been assigned to a user, and is structuredsuch that the relative users' positions in the bitmap are associatedwith some resource allocation. In some embodiments, the relative users'positions in the bitmap are also associated with “user groups”. That isto say, each position in the bitmap is associated with a user group, andthe users belonging to a specific group can be uniquely identified bytheir position in the bitmap.

A specific example is illustrated in FIG. 9. Here, there is a 16 bitbitmap containing a respective bit for each of 16 users. Each “usergroup” consists of the set of positions that are separated by four bitpositions in the bitmap. Thus “user group 1” is positions 1,5,9,13;“user group 2” is positions 2,6,10,14 and so on. More generally, theallocation of bitmap positions to user groups can be arbitrarilydefined.

In some embodiments, a “user group” is defined as a group of users whohave their first HARQ sub-packet transmission occurring in the same slotwithin a HARQ interlace as described in detail with reference to theexample of FIG. 1.

The value at a position in the bitmap, indicates whether or not aresource has been assigned to the user associated with that bitmapposition. The bitmap can contain positions for all or some users in thesystem. There may be multiple bitmaps for different sets of users, eachbitmap having associated groups.

In some embodiments, users are assigned to the same bitmap on the basisof commonality among factors such as long-term channel condition,modulation and coding scheme (MCS), resource allocation size, etc.

In the context of embodiments where the spreading of the firstsub-packet transmissions for multiple wireless stations across a VoIPframe is performed, there will be a number of positions that the firstsub-packet can be. In some embodiments, bitmap positions for differentusers in the same group are separated by the total number of possiblestart points for a given HARQ interlace. For the example of FIG. 9, thiswould be true for an implementation in which there are four positionsfor first sub-packet transmission (consistent with the example of FIG.1).

In some embodiments, the separation is equal to the total number oftransmissions allowed per packet. In some embodiments, the number oftransmissions allowed per packet is the same as the number of startpositions for first sub-packet transmission.

The bitmap described above is for a single interlace, however a singlebitmap can have information for more than one interlace. Each interlacemay refer to a respective slot, of a set of grouped slots. In this case,the users belonging to the same group can be separated by a total numberof possible start positions per interlace multiplied by a number ofinterlaces assigned by the bitmap.

Such a bitmap can also be used to indicate that a user's resources arein use. The bitmap supports re-packing of resources even with persistentallocation. Detailed examples are given below.

Addition of New Users to Bitmap

In some embodiments, new users are added at the end of the bitmap (andvacant spots in bitmap) in such a manner as to ensure uniformdistribution of users across groups and to allow the assignment of auser to a group without additional signalling.

Non-Persistent Assignment Using Bitmap

In some embodiments, a bitmap is used to indicate non-persistentresource assignments. A bitmap is created, with the bitmap indicatingwhich users will be assigned resources in the slot. This step is beingdescribed first, but the order is not important.

In some embodiments, the non-persistent assignment is done groupwise. Inthe event groups are not defined, the following approach can be usedwith all the users in one group.

Users in a first “user group” are processed first for the purpose ofresource allocation. The first user group can be arbitrarily defined. Insome embodiments, the first user group contains users that are toreceive a first HARQ sub-packet transmission in the current slot.

The resources are allocated in a predetermined manner to users that areto be scheduled as indicated by the bitmap. The predetermined manner isknown to the transmitter, and is known to the receiver such that anyreceiver can read the bitmap and determine if and where its allocatedresource is. In the examples that follow, first, second . . . Nthresources are allocated. These resources are known to receivers suchthat if a given receiver is allocated the first resource, it knows whatthat is. Note that the sequence “first”, “second”, “Nth” does notnecessarily imply any temporal and/or frequency relationship between theresources.

The following allocation method is described from the perspective of areceiver reading the bitmap. Of course, the transmitter is responsiblefor generating the bitmap, and for transmitting packets to theappropriate users using the resources thus allocated. The bitmap is readby starting at the position of the first user in the first user group(for example the user group that is receiving its first HARQ sub-packettransmission in the current slot). If the bitmap indicates that aresource is to be allocated to the first user, then the first resourceis allocated to this user. If the bitmap does not indicate a resourceallocation to the user, the first resource is available to be assignedto the next user.

The next position read is that of the second user belonging to that usergroup. If the first resource was assigned via the bitmap in the previousstep, the next resource (second) is assigned to this user. If resourceswere not assigned to the first user, than the second user is assignedthe first resource.

Each user from this first “user group” is assigned resources in thismanner. Each user, that is assigned resources via the bitmap, isassigned the next available resource.

Users from the next group are assigned resources in the manner as thefirst. Those users assigned resources will occupy the “next” resourcesafter the last assigned resources. This process is continued until allusers from all groups have been processed.

FIG. 10 shows a first example of resource assignment for the bitmap ofFIG. 9, where numbers indicate which resource has been assigned for thecase where the current slot is a slot in which users of “user group 1”are receiving its first HARQ sub-packet transmission. For user group 1,assumed to include users 1, 2, 3 and 4, it can be seen from the bitmapof FIG. 9 that only users 1, 3 and 4 are allocated resources. Thus, inthe assignment of resources shown in FIG. 10, the first, second andthird resources 352,354,356 are allocated to users 1, 3 and 4respectively. Similarly, for the second user group, FIG. 9 shows thatonly user 7 is to be allocated a resource. Thus, in FIG. 10 in theordering of resources, the fourth resource 358 is allocated to user 7.The bitmap of FIG. 9 shows that for user group 3, users 9 and 11 are tobe allocated resources. Thus, in FIG. 10, resources 360,362 areallocated to users 9 and 11 respectively. Finally, in user group 4, thebitmap of FIG. 9 shows that users 13, 14 and 16 are to be allocatedresources. The resource mapping of FIG. 10 shows that the seventh,eighth and ninth resources 364,366,368 are allocated to users 13, 14 and16 respectively.

FIG. 11 shows a second example of resource assignment for the bitmap ofFIG. 9, where numbers indicate which resource has been assigned for thecase where resource assignment starts with the users of user group 2,for example if they are receiving their first HARQ sub-packettransmission in the current slot.

Having generated the bitmap, and performed the allocations, thefollowing is an example of a specific method of users determining theirnon-persistent assignment from the bitmap thus transmitted.

For a user in the user group receiving its first HARQ sub-packettransmission, the user determines whether resources have been assignedto it via the bit indicator at the position corresponding to it. Ifresource assignment is indicated by the bitmap, the user's resourcelocation is determined as follows: the bitmap is read starting from theposition of the first user in the group receiving its first HARQsub-packet transmission, followed by the next user in that group, and soforth until the position corresponding to the given user is reached. Auser in this group reads the bitmap noting the number of resourcesassigned before the user's position in the bitmap, given the method ofreading the bitmap described. Given the resource assignments to otherusers in bitmap positions before it, the user identifies its resourcesas the next resource segment immediately following those alreadyassigned.

For a given user in any other group, the user determines whetherresources have been assigned to it via the bit indicator at the positioncorresponding to it. If resource assignment is indicated by the bitmap,the user's resource location is determined as follows: A user in a givengroup reads the bit map noting the number of resources assigned beforethe user's position in the bitmap, given a certain method of reading thebitmap. The bitmap is read starting from the position of the first userin the group receiving its first HARQ sub-packet transmission, followedby the next user in that group, and so forth until all users in the thatgroup have been read. The next position read is that of the first userin the next group, and follows as before for all users in this group.The bitmap is read in this fashion until the position for the given useris reached. Given the resource assignments to other users in bitmappositions before it, the user identifies its resources as the nextresource segment immediately following those already assigned.

Persistent Assignment Using Bitmap

In some embodiments, the bitmap is used to perform persistent resourceassignment. At the transmitter, a bitmap is created, with the bitmapindicating which user will be assigned resources in the slot. Users inthe “user group” that is receiving its first HARQ sub-packettransmission in the current slot are processed first. If a user in thisgroup is to be assigned resources, the user is assigned in a knownlocation associated to its order in the group, which is not dependent orwhether other users in the group have been assigned resources. Forexample, the 3^(rd) user in the group might be assigned the 3^(rd)resource segment, regardless of whether or not the 2^(nd) resource wasassigned to a user in this group. In other words, these resourcepositions are not re-packed as in the previous non-persistent resourceassignment example.

Users from the next “user group” are now assigned resources. Each userthat is assigned resources via the bitmap is assigned to the nextavailable resources starting with any available resource not assigned tothe first group. This process is continued until all users from allgroups have been processed. In other words, the packing approachdescribed previously is applied for groups other than the first group.

In the case of persistent assignment, each user in the user groupreceiving its first HARQ sub-packet transmission has a known locationfor its resources as described in the resource allocation method.

The user can determine whether resources have been assigned to it viathe bit indicator at the position corresponding to it, if the bitmap isavailable. If the bitmap is unavailable due to error or otherwise, usersin this group do not have to read the bitmap as resource allocation isknown, and the user will assume it has been assigned resources in thislocation as the default operation. The user may unsuccessfully try todecode packet intended for a different user. Even though it is notrequired, users in this group may read the bitmap for other purposessuch as tracking resource allocation of other users.

For a given user in any other group, the user determines whetherresources have been assigned to it via the bit indicator at the positioncorresponding to it. If resource assignment is indicated by the bitmap,the user's resource location is determined. A user in a given groupreads the bit map noting the number of resources assigned before theuser's position in the bitmap, given a certain method of reading thebitmap. The bitmap is read starting from the position of the first userin the group receiving its first HARQ sub-packet transmission, followedby the next user in that group, and so forth until all users in the thatgroup have been read. The next position read is that of the first userin the next group, and follows as before for all users in this group.The bitmap is read in this fashion until the position for the given useris reached. Given the resource assignments to other users in bitmappositions before it, the user identifies its resources as the nextresource segment immediately following those already assigned.

A specific example of this type of persistent resource assignment, againassuming the bitmap of FIG. 9, is shown in FIG. 12 for the case wherethe current slot it the slot in which the users of “user group 1” arescheduled first, for example if they are receiving their first HARQsub-packet transmission during the current slot. In this example, theusers of group 1 are assumed to be persistently assigned the first fourresources 370,372,374,376. However, as indicated by the bitmap of FIG.9, only users 1, 3 and 4 are actually to be allocated resources, and assuch they are allocated the first, third and fourth resources370,374,376. The second resource, 372 is available for re-assignment toanother user. The allocation continues with the next user group namelyuser group 2, and the first user to be allocated a resource there isuser 7 and as such that user is slotted into the second resource 372.The remaining resources are allocated as described previously fornon-persistent allocations.

A specific example of this type of persistent resource assignment, againassuming the bitmap of FIG. 9, is shown in FIG. 13 for the case wherethe current slot it the slot in which the users of “user group 2” arescheduled first, for example if they are receiving their first HARQsub-packet transmission during the current slot. For this example, foruser group 2, only user 7 is to be allocated resources and itspersistent allocation will be in third resource 374. The remainingresources persistently allocated to the second group, namely resources370,372,376 are available for re-assignment to non-persistent users ofthe next group.

More generally, if the bitmap indicates that a receiver is to receive aresource allocation, a receiver determines from the bitmap the resourcesallocated to persistent receivers and to previous allocations tonon-persistent receivers, and processes a next resource that has notbeen allocated as the non-persistently allocated resource for thatreceiver.

An additional example order of reading the bitmap in is to first assignresources to the user group having their first HARQ transmissionopportunity. If the resources are persistently assigned for the firsttransmission they will be in a known location. The remainder ofassignments are processed observing what assignments are available ornot available based on the assignments for all users in the user groupthat is having its first HARQ transmission, and then assigning resourcesin sequential order from the beginning of the bitmap. If an assignmentis indicated, a user is assigned the first available resource.

In some embodiments with persistent assignment of a first HARQtransmission, the number of possible start points for transmitting a newpacket, or interlace offsets, may be different from the number of HARQtransmissions of a packet. That is, even though an interlace in aparticular slot is identified as a possible start point for a firsttransmission, the interlace may be used for further re-transmissions ofsub-packets if the packet being transmitted has not been properlyreceived. An example is described below in detail with reference to FIG.30. In some cases, more than one transmission of a packet may bepersistently assigned. The frequency of the persistent assignments maybe equal to the number of VoIP interlace offsets.

As an example, if the number of VoIP interlace offsets is three, and thenumber of HARQ transmissions is five or six, than the first and fourthtransmission can be persistently assigned.

Addition of Users to the Bitmap

In some embodiments, users are added to the bitmap in ways that do notimpact the bitmap positions of users who have previously been assigned aposition. In some embodiments, new users can be added to the end of thebitmap. In embodiments in which the bitmap positions within each groupare separated by a spacing equal to the number of groups, this willresult in a uniform distribution of users over the different first HARQsub-packet transmission positions. In some embodiments, users can alsobe added into vacant bitmap positions created by a user leaving (orbeing deleted from) the bitmap. This does not effect bit map positionsof existing already assigned users that are not being deleted.

With the user group definition presented above, a user can therefore beassigned to a user group, strictly from their position in the bitmapwithout the requirement for additional signalling.

Temporary Allocation of Resources to Users Who are not Part of theBitmap

Some embodiments allow for the temporary allocation of resources toreceivers that are not part of the bitmap. The base station maydetermine a particular receiver identified in the bitmap does notrequire resources in a given slot. In this case, the resources can beallocated to a receiver that is not part of the bitmap. This receivercan be signalled by some other method such as another bitmap, anothergrouped control, unicast control channel, or some other mode.

The receiver can determine the location of the allocation by reading thebitmap in the manner described for receivers who are part of the bitmapor through the use of another form of signalling with channelidentification such as combination index, or node ID, etc.

The bitmap will indicate that the resource has been assigned, so thatusers reading the bitmap will know it is occupied by some other user andfactor that in accordingly in determining their own resourceallocations. The user whose bitmap position is associated with theresource in this slot will unsuccessfully attempt to decode thetransmission.

Full Persistent Resource Allocation

In some of the embodiments described, persistent allocation of resourcesfor the first transmission is provided for at least some of the users sothat such users will not have to successfully receive the bitmap inorder to receive the first HARQ transmission.

In another embodiment, for some users, persistent assignment is providedfor the first transmission and subsequent HARQ retransmissions. Thiswill be termed ‘full persistent allocation’. This feature can be used tosupport some users with poor channel conditions. Furthermore, in someembodiments users receiving single frequency network (SFN)transmissions, possibly during soft-handoff with other sectors or cells,are also be supported using this feature.

Combined Bitmap for Fully Persistent Users and Persistent FirstTransmission Users—First Example

In some embodiments, a first subset of users are fully persistent, and asecond subset, possibly all remaining users, have a only their firstallocation a persistent first allocation.

In an example of full persistent allocation using a combined bitmap, theusers with full persistent allocation for all HARQ transmissions aredesignated as a special user group in the bitmap. The users' positionsin bitmap could be all at the beginning, or distributed throughout thebitmap in some known way. In some embodiments, a separate bitmap isemployed. The locations in the bitmap are known for all other users tosee. In some embodiments, the number of the first subset is fixed, andin known locations, so that all users can tell which bits in the bitmaprelate to full persistent resource allocations.

In some embodiments, the full persistent allocation users are furthersegmented into groups that have different HARQ sub-packet start points,as described for other embodiments above. With this approach, users aredistributed across multiple groups so that a different group starts apacket transmission at a different slot in the same interlace. For fullpersistent allocations, the resource allocation is a fixed and knownresource allocation for each HARQ transmission, and the resourcelocation is unique for each user.

In some embodiments, SFN can be supported for all HARQ transmissions byassigning the same resources to a single receiver across multiplesectors or cells.

For the remaining user groups, only the first HARQ transmission is apersistent assignment. Assignments for this case can be the same asdetailed above and involve persistent first transmission allocation foreach group in a different slot of the interlace. Re-packing of otherusers groups in free resources can be performed. Persistent locationsare fixed for the users receiving their first transmission.

In some embodiments, the resource locations for the first transmissionpersistent allocation are immediately after the resource locations ofthe users with persistent allocation for all HARQ transmissions. Moregenerally, the persistent allocations simply need to be located in amanner known to both the transmitter and receiver.

The unused (not allocated) resources for one or both of a) the userswith persistent allocation for all HARQ transmissions and b) the userswith persistent allocation for the first HARQ transmission can bere-packed and reassigned to other users. Users can determine whatresources are not assigned by reading the bitmap, and deriving thelocation of the free resources.

Combined Bitmap for Full Persistent Users and Persistent FirstTransmission Users—Second Example

In a second example of the use of a combined bitmap for full persistentusers and persistent first transmission users, a cyclic shift withinfull persistent resources is employed.

More generally, for any of the embodiments described herein, a cyclicshift can be performed for any resource allocation, meaning that thelocation of a resource associated with particular signalling will movecyclically through the available resource. More generally still, for anyof the embodiments described herein, an arbitrary shift of the resourceallocation can occur, so long as the shift is known to both thetransmitter and receiver.

In an example of full persistent allocation using a combined bitmap, theusers with full persistent allocation for all HARQ transmissions aredesignated as a special user group in the bitmap. The users' positionsin the bitmap could be all at the beginning, or distributed throughoutthe bitmap in some way. In some embodiments, a separate bitmap isemployed. The locations in the bitmap are known for all other users tosee.

In some embodiments, the full persistent allocation users are furthersegmented into groups that have different HARQ sub-packet start points,as described for other embodiments above. With this approach, users aredistributed across multiple groups so that a different groups starts apacket transmission at a different slot in the same interlace. Theresource allocation is a fixed and known resource allocation for eachHARQ transmission, and the resource location is unique for each user.

In some embodiments, SFN can be supported for all HARQ transmissions byassigning the same resources to a single receiver in multiple sectors orcells.

For this embodiment, the location of the full persistent resource shiftsin each slot within a set of resources for this user type. For exampleif a set of four resources 1,2,3,4 (not necessarily contiguous) havebeen allocated for full persistent users, then the mapping could be:

slot 1: user 1→resource 1

-   -   user 2→resource 2    -   user 3→resource 3    -   user 4→resource 4

slot 2: user 1→resource 2

-   -   user 2→resource 3    -   user 3→resource 4    -   user 4→resource 1

slot 3: user 1→resource 3

-   -   user 2→resource 4    -   user 3→resource 1    -   user 4→resource 2

slot 4: user 1→resource 4

-   -   user 2→resource 1    -   user 3→resource 2    -   user 4→resource 3        For this example, it is assumed the users all have their        original sub-packet transmission during slot 1, and that slots        2,3,4 are available for retransmissions if necessary. Resource        locations are known for each user and each HARQ transmission,        however the locations cyclically shift with the HARQ. This does        not require the fully persistent users to read the bitmap as        locations are known for each HARQ transmission.

In some embodiments, users with persistent assignment for all HARQtransmissions, but who are receiving their first HARQ sub-packettransmission, are assigned the ‘first’ resources in a given slot, but inany case persistent for this example.

In some embodiments, users receiving their second HARQ sub-packettransmission in the given slot are assigned the ‘next’ set of resources,etc, but in any case persistent for this example.

It is to be understood that while cyclic shift of resources is describedin this embodiment, other resource shifting patterns can be usedprovided they are known at the receiver and transmitter.

For the remaining user groups, only the first HARQ transmission is apersistent assignment. Assignments for this case can be the same asdetailed above and involve persistent first transmission allocation foreach group in a different slot of the interlace. Re-packing of otherusers groups in free resources can be performed. Persistent locationsare fixed for the users receiving their first transmission.

In some embodiments, the resource locations for the first transmissionpersistent allocation are immediately after the resource locations ofthe users with persistent allocation for all HARQ transmissions.

In some embodiments, SFN can be supported for the first HARQtransmission by assigning the same resources to a single receiver acrossmultiple sectors or cells for the first transmission.

The unused (not allocated) resources for one or both of a) the userswith persistent allocation for all HARQ transmissions and b) the userswith persistent allocation for the first HARQ transmission can bere-packed and reassigned to other users. Users can determine whatresources are not assigned be reading the bitmap, and deriving thelocation of the free resources.

Multiple Resource Assignment to a Single Persistent Resource

In some embodiments, multiple users may be assigned the same resourcesduring persistent allocation. In these embodiments, the persistentresource for each user is known, but is not unique. Only one user willreceive transmissions on this resource in a given slot.

Each of the users which have the same persistent resource have anindividual entry in one or more assignment bitmaps. One bitmap isassumed in the following examples.

The bitmap assigns persistent resources from some start point to usersbased on bitmap position and user groups. Multiple positions in thebitmap refer to the same resource. For example, in some embodiments afirst set of bitmap positions refer to set of resources starting from astart point, and then a second set of bitmap positions that may followthe first set refers to the same set of resources starting again fromthe start point. In this manner, multiple bitmap positions can refer tothe same resource. The point in the bitmap where this occurs can besignalled with any useful timing, for example often, occasionally.Alternatively, the point in the bitmap where this occurs may be fixedand/or derived from system parameters.

The bitmap will indicate to other users which of the multiple usersoccupies the resource. Each of the multiple users can determine if thetransmission on the resources is their own by a) attempting to decodethe resources and failing (and possibly continuing to do so for allre-transmissions) or b) reading the bitmap and determining the resourcesare assigned to another user. A bitmap may not be necessary for theseusers. However, the bitmap will be useful for other users as detailedbelow.

Users that are not receiving a persistent assignment in the slot can beassigned a persistently assigned resource if it is not assigned to anyof the persistent users. For these users, the resource location isderived from the bitmap. For example, unused persistently assignedresources are allocated in sequence to users that are not receiving apersistent assignment. The same or a different bitmap may be used tosignal resource allocation to these additional users. After all thepersistent assignments are used up, additional non-persistently assignedresources may be allocated non-persistently, again using the bitmap.

In some embodiments, the same resource can be persistently allocated tomultiple users for a first HARQ transmission. In some embodiments, thesame resource can be persistently allocated to multiple users for somenumber of HARQ transmissions, possibly all HARQ transmissions.

Additional Comments

Resources are ordered in some manner so that it is known which resourcesthe “first” and “next” resources. This order is arbitrarily defined. Forexample, the first resource maybe known or signalled by some othermethod. Resources refer to physical or logical resources, and can bedistributed or concentrated in any manner. Each resource can consist ofone or more logical resource elements. The size of each resource can bepre-determined and known for all users, or associated with this bitmap(as there may be other bitmaps associated with other parameters in thesame system), or determined by another bitmap, or signalled in someother manner Resources do not have to be all the same size.

It can be seen that a starting point for reading the bitmap changes witheach slot, as in different slots a different group will receive itsfirst HARQ sub-packet transmission. Alternatively, it is also possibleto transmit the bitmap in such a manner that it always starts with thebit-position of the first user in the “user group” that will receive itsfirst HARQ sub-packet transmission in the given slot.

For most receivers, the process for reading the bitmap at a receiverstarts by determining if resources have been assigned to the receiver,and then determining what resources have been assigned to other users.Alternatively, the receiver may read the bitmap, determining resourceallocation to other receivers prior to determining if resources havebeen assigned to it.

The bitmap can also be interpreted in other ways and associated withresource allocation at the transmitter and the receiver so long asallocation is consistent with the group definition, e.g. persistent vs.non-persistent.

In some embodiments, the relative bitmap positions of users may not beassociated with “users groups”. The assignment of resources to users mayfollow an order not related to user groups. Assignment may be consistentwith persistent with or non-persistent assignment, whicheverappropriate, for a given user in a given slot.

The same bitmap is used for many of the examples presented above forsimplicity. In normal operation the bitmap may change every schedulingperiod, for example each slot, a slot being a portion of a frame duringwhich the entire content of a VoIP packet can be transmitted.

For non-persistent allocation, the start position and order of readingthe bitmap is arbitrary provided that both receivers and transmitterhave knowledge of the order. The allocation or placement of any resourcecan be changed as often as every scheduling period.

For persistent allocation, the order of reading the bitmap is arbitraryprovided that 1) both receivers and transmitter have knowledge of theorder 2) users that are receiving their first HARQ sub-packettransmission receive allocation in a known location. The allocation orplacement of any resource can be changed as often as every schedulingperiod.

The creation, reading, interpretation and/or deviation of the bitmap isarbitrary so long as the transmitter and receiver are aware of at leastpart of the process and the methods of persistent and/or non-persistentallocation, whichever may apply, are followed.

In some embodiments, a user can be assigned a persistent resource forone or multiple HARQ transmissions, and a non-persistent resourceindicated by the assignment bitmap for those HARQ transmissions whichare not assigned persistent resource.

As an additional example of bitmap organization, each user group mayoccupy a set of consecutive bitmap positions. The first set of positionsmay be bitmap positions that correspond to users in user group 1, thenext set of positions may correspond to user group positions, and so on.

In some embodiments, the organization of the bitmap positions may bechanged as often as every slot.

The separation of users belonging to the same user group in the bitmapis arbitrary and does not need to be regular, so long as the positionsare understood by the transmitter and receivers.

In some of the described embodiments, a persistent allocation isprovided only for the first HARQ transmission. In other embodiments,persistent allocation is provided for more than just the first HARQtransmission, optionally all of the HARQ transmissions for some or allreceivers.

In some embodiments where persistent allocation is used for at leastsome HARQ transmissions for the purpose of SFN across sectors or cells,each sector may use identical resource allocation for at least some HARQtransmissions for these users so that a composite signal from at leastsome of the sectors or cells is received on the allocated resource atthe receiver.

In some embodiments that include persistent allocation for one or moreHARQ transmissions, it is possible that one or more groups can havetheir first HARQ sub-packet transmission in a given slot. Thesub-division of these groups for services (possibly SFN) or classes isarbitrary. Each of these persistently allocated groups can be allocatedone of the ‘first’ sets of resources (contiguously, or otherwise),followed by the re-packing and assignment of unassigned or ‘free’resources to other users in that slot.

As a specific example, in a configuration with three possible first HARQtransmission start positions, a bitmap may contain five user groups.Three user groups may be for wireless station with persistentlyallocated resources for the first HARQ transmissions, with each groupcorresponding to a different start position. The other two may be forwireless stations without persistent assignment for any HARQtransmission. The groups without persistent assignment may or may not beassociated with a particular start point for the first HARQ packettransmission.

Various other specific examples will now be presented with reference toFIGS. 14 to 18.

FIG. 14 shows an example of non-persistent assignment using a sequentialreading of bitmap. The resource assignment is a based on the bitmap ofFIG. 9. Numbers indicate which users have been assigned. Again, theassumption is that the current slot is the slot in which “User group 1”is receiving its first HARQ sub-packet transmission.

FIG. 15 is another example of non-persistent assignment using asequential reading of bitmap. Resource assignment is again based on theexample bitmap on FIG. 9. Numbers indicate which users have beenassigned. The current slot is the slot in which “Users group 2” isreceiving its first HARQ sub-packet transmission. However, in this casethe sequential reading starts with user 1 with the result that thebitmap is the same as FIG. 14.

FIG. 16 shows an example of non-persistent assignment using sequentialreading of the bitmap. Resource assignment is again based on the examplebitmap of FIG. 9. Numbers indicate which users have been assigned. Thecurrent slot is the slot in which “Users group 2” is receiving its firstHARQ sub-packet transmission. In this case, the sequential readingstarts with user 5. FIGS. 14,15,16 illustrate the arbitrariness of atwhich user the sequential reading starts.

FIG. 17 shows an example of persistent assignment using sequentialreading of the bitmap. Resource assignment is again based on the examplebitmap of FIG. 9. Numbers indicate which users have has been assigned.The current slot is the slot in which “User group 1” is receiving itsfirst HARQ sub-packet transmission. In this example, users 1, 3 and 4have a persistent assignment and are not re-packed. Persistentassignments that are not used are available for re-assignment (shown asa blank or re-assigned).

FIG. 18 shows an example of persistent assignment using sequentialreading of the bitmap. Resource assignment is again based on the fromexample bitmap of FIG. 9. Numbers indicate which user has been assigned.The current slot is the slot in which “Users group 2” is receiving itsfirst HARQ sub-packet transmission. In this case, user 7 has apersistent assignment. Persistent assignments that are not used areavailable for re-assignment (shown as a blank or re-assigned).

Multiple Concurrent Allocations

Some embodiments of the invention can be applied to any grouped resourceallocation scheme and includes those signalled by a bitmap, combinationindex, or other methods. In some embodiments, there are multiple groupsthat are concurrently being allocated, for example using multiplebitmaps, combination indexes or other methods. In the embodimentsdescribed below, multiple bitmaps each associated with a respective setof users are contemplated, but more generally they can be applied toother allocation schemes as well.

For each bitmap, a set of resources is assigned. After allocation andrepacking, some of these resources may remain unused. In someembodiments, users from another bitmap can be assigned resources fromthese unused resources. In some implementations, users that arereceiving such unused resources will need to read their own bitmap andthe bitmap of others to determine where their resources are. Usersallocated in the first such bitmap will only need to read their ownbitmap to figure out their resource allocations. Users allocated in thesecond bitmap will need to be able to read the first bitmap and theirown bitmap to figure out their resource allocations and so on untilusers allocated in the last bitmap will need to be able to read all ofthe bitmaps to figure out their resource allocations.

In some embodiments, where there are multiple bitmaps being used toallocate resources, the bitmaps are allocated in sequence according tosome criterion. For example, the resource allocation may begin with thebitmap associated with users with the worse channel conditions, and thenproceed in sequence according to channel conditions until concludingwith the allocation for the bitmap associated with users with the bestchannel conditions. This is advantageous because a user with poorchannel conditions will only have to read its own bitmap, and it shouldbe able to read its own bitmap assuming that bitmap is sent withsufficient power, but the same user may not be able to read a bitmapsent for other users as the bitmap for others may have been sent withless power accounting for the better channel conditions beingexperienced by the other users. Thus, if a user with poor channelconditions is allocated in a later bit map, that user may not be able toread all of the bitmaps required to figure out its resource assignment.Assigning the users with poor channel conditions first avoids thisproblem.

In some embodiments, where multiple bitmaps are employed, resourceallocation of the next bitmap begins with unused resources of theprevious bitmap.

In some embodiments, only those users not receiving persistentallocation are repacked into unused resources of another bitmap.

In some embodiments, users of a given bitmap are repacked only withinthe resources assigned to that bitmap. Unused resources may bere-assigned to non-persistent users that are not part of the bitmap.Such re-assignment may be signalled by some other method.

Bulk Resource Allocation

In some embodiments, a user may be allocated a bulk resource by startingwith a first resource allocation from which a subset is removed due toits having been assigned to other users by a bitmap, grouped signallingscheme, or some to other scheme. The user can derive which resources arealready assigned to other users from knowledge of the first resourceallocation and the bitmap, bitmaps, or other assignment schemesignalling the subset to be removed. What is left over after thisremoval is what has been allocated to that user. For example, a firstuser may nominally be allocated a set of 20 DRCHs in a slot. Then, otherusers are assigned individual DRCHs in the same slot. The first userexamines these assignments of individual DRCHs to other users, anddetermines the remaining ones of the 20 DRCHs to be its own resourceallocation.

In some embodiments, a non-persistent user with favorable channelconditions can be assigned resources in this manner as these users aremore able to correctly receive the bitmaps of other users.

In some embodiments, in order to avoid the necessity of such users toalways examine the bitmaps of other users, a field in the assignmentsignalling can be used to indicate whether or not the user must alsoread the bitmap(s), or other signalling scheme intended for other users,in order to derive which resources have already been assigned to otherusers.

For example a single bit field might be used to indicate either 1) theuser is allocated all resources specified excluding those allocated toother users or 2) the bitmap does not need to be read as all resourcesspecified are assigned to the user.

In some embodiments, a user can be assigned unused resources, possiblyin addition to other resources, from grouped scheme using a unicastsignaling message. As an example, a unicast SCCH (shared controlchannel) assignment message for a user indicates a bulk set ofresources. The bulk set of resources may be indicated, for example by achanID (channel identification) field in a FLAM (forward link assignmentmessage). A bit field of the SCCH may indicate if checking the groupresource assignments is required. The location of the signalling schememay also be signalled. The user may also read the grouped resourceallocation bitmap, or bitmaps, to determine what portion of the resourcehas been assigned to other users, and subtract these resources from itsbulk assignment indication.

In some embodiments, it is understood that grouped resource assignmentsmay change for each HARQ transmission. It is also possible that for someor all HARQ transmissions, including the first, the grouped resourcesassignments do not conflict with the bulk resources assignment.

In some embodiments, unicast signalling is used for the bulk resourceassignment methods, and grouped resource allocation signaling may becomprised of a bitmap, or bitmaps.

In some embodiments, for a HARQ transmission of a packet, there arecases which correspond to receiving a signaling message or not receivingit. These cases can apply to the same transmission as a user may receivean assignment signal for none of or one or more of its re-transmissions.

As will be described below in further detail, in some embodiments it maybe desirable to configure HARQ transmissions into portions which are a)transmitted using unused grouped signalled resources and b) transmittedover a non-shared resource space. In some other cases, the packettransmission may be contained in only one of shared or non-sharedresources.

In some embodiments when a signalling message is received, the bulkresource assignment indication is processed in a manner by removingresources assigned to other users by a grouped signalling method. Insome embodiments, the resultant resource assignment may be a differentresource size then previous transmissions.

In some embodiments, a different packet format, and/or MCS may be usedin comparison to a previous transmission. The change in packet formatand/or MCS may be signalling in a signalling message. In someembodiments, the signalling to the user is a unicast SCCH signal withthe chanID field and a PF (packet format) field in the FLAM. RAS-HARQ(resource adaptive synchronous-HARQ) support may be enabled.

In other embodiments when a signalling message is received, the resourceassignment may be of the same size as a previous transmission. Forexample, a unicast signalling message may be used to indicate the bulkresource assignment.

In some embodiments, when a signaling message is not received, the usermay continue to use the same resource(s) for the retransmission orretransmissions. The user may not have to determine grouped resourceassignments for each of its retransmissions, after determining this forthe first HARQ transmission. In some embodiments, the resources used bythis user for transmissions are indicated as unavailable to usersreceiving assignments from the grouped resource allocation signaling.

In some embodiments when a signaling message is not received, the usermay use the same amount of resources as assigned for a previous HARQtransmission. The user may observe the grouped resource assignments forthe transmission opportunity, and determine which resources areavailable. In some cases, the user may determine the ‘first’ resourcesavailable have been assigned to it. In some embodiments, the user maylimit its assignment to be within the previous bulk resource assignment.Furthermore, the assignment size may be the same size as a previoustransmission, or different.

In some embodiments, as will be described in detail below, when asignalling message is not received, the user may assume there is noportion of the shared resource space for group resource allocationassigned to it for this transmission.

Transmission Power

In some embodiments, the maximum transmit power to a given user iscapped at a level related to the longer term channel conditions, such asaverage signal to noise ratio or geometry (path loss and shadowingconditions), of the user. In some embodiments, the relationship is aninverse relationship. An OFDM signal may contain allocations to multipledifferent users with each allocation having a different transmit power.

In a specific example of this, the maximum transmit power to a userduring power control operation is limited to a fixed value, such as 3dB, above the inverse of the geometry of the user.

In some embodiments, additional signalling, for example a second bitmap,is used to indicate the size of a resource and/or MCS's for each userassigned by a first bitmap. The second bitmap might for example containa bit for each user that is actively being assigned by the first bitmapto indicate small or large resource assignment. As in other embodiments,a single bit per entry is the most efficient, but larger fields may beemployed at the expense of increased overhead.

In some embodiments, the second bitmap may always contain entries forpersistently assigned users, regardless of whether or not they areassigned. The size of the persistently assigned resource is alwayssignalled in this case. In this case, the other users can derive wheretheir resources are from the second bitmap.

In some embodiments, the second bitmap does not contain entries forpersistently assigned users. In this case, there would be an assumeddefault size for a persistent resource allocation.

In some embodiments, there are separate bitmaps for each HARQ interlace.In some embodiments, some users may be assigned to multiple positionsthereby providing the option of increased bandwidth to such users. Thesemultiple positions can be on one or more bitmap, and can be in one ormore user groups.

In some embodiments, a user group refers to a set of users having thesame start position of the first HARQ transmission of a sub-packet for agiven interlace.

Primary and Secondary Assignments

In some embodiments, users can be assigned to a bitmap, and possibly auser group, for a primary assignment, and another position on another orthe same bitmap, in another or the same user group, for the purpose of asecondary assignment. These assignments may be on the same or differentHARQ interlaces.

Assignments may be persistent for all transmissions, persistent for thefirst transmission, persistent for at least one transmission ornon-persistent for all transmission. Assignments may consist of bitmapor other methods of signalling for one or more transmissions for thepurpose of resource re-packing or otherwise.

In some embodiments the first transmission may be persistently assignedfor either the primary or secondary assignments, or both.

In some embodiments, the secondary assignment may be shared by more thanone user while the primary assignment is unique. In case of persistentassignment with bitmap signalling, multiple positions on the bitmapassigned to different users are associated with the same persistentresource. The bitmap indicates which user is assigned resources. In someembodiments, this applies to persistent allocation of one or moretransmissions.

In some embodiments, a primary or secondary assignment refers to abitmap position associated with an interlace and first sub-packettransmission's start position. An assignment can follow the rules ofpersistent first slot assignment, and further assignments by the bitmapfor other transmissions as described previously. Transmission of anassignment may occur in the same interlace until finished, orassignments are switched.

In some embodiments, the user will be assigned its primary resources bythe bitmap for a given transmission. The user may also be assigned adifferent transmission on its secondary resources. The start slots andinterlaces may be different for the primary and secondary interlaces.

In some embodiments, a packet that begins transmission for the primaryassignment continues all re-transmissions using the allocations for theprimary assignment. The packet that begins transmission for thesecondary assignment follows assignments for the secondary assignment.The secondary assignment may or may not be present.

In some embodiments, the resources are persistently assigned for thefirst transmissions on one or both primary and secondary assignments.

In some embodiments with persistent allocation of the first sub-packettransmission, the user can receive the first transmission and attempt todecode it. If the user cannot, the user will store the information anduse it the decoding attempts of further transmissions until 1) the useridentifies the packet is not intended for it by assignment signalling(bitmap or otherwise) or another means, 2) the packet finishes themaximum number of transmissions and/or 3) the packet is decodedsuccessfully.

In some embodiments with shared secondary persistent assignments, thesecondary assignment may be assigned to another user.

In some embodiments the shared secondary persistent assignment is usedwhen there are more re-transmissions required, or additional packets fortransmission due to packet buffer jitter.

An example is depicted in FIG. 19. A primary assignment is shown in thetop row, this consisting of a repeating pattern having a persistentassignment followed by five non persistent assignments all for a givenuser. The persistent assignment is used for the first transmission of apacket, and the remaining assignments are for re-transmission asrequired. The secondary assignment is shown in the bottom row. There isa persistent assignment followed by non-persistent assignments forretransmission as required. In some embodiments, even though the firstassignment on the primary and secondary assignment is persistent, one orboth of these first assignments are shared as described for previousembodiments. The need to use the secondary assignment may result frommore packets arriving than can be accommodated by the normal persistentassignment, for example due to packet buffer jitter.

FIG. 19 also illustrates the general concept that the start times,interlacing structure, etc. can be defined differently for the secondaryassignments than for the primary assignments.

In some embodiments, a packet that begins transmission for the primaryassignment will switch to the secondary assignment after some number ofre-transmissions. In some embodiments, this switch occurs at the startpoint of the secondary assignment. A new packet can begin transmissionsusing the primary assignment.

In some embodiments, resources are persistently assigned to the firsttransmission of the primary and secondary assignments, where the firsttransmissions of the secondary assignment may not be the firsttransmission of the packet.

An example is depicted in FIG. 20. A primary assignment is shown in thetop row, this consisting of a repeating pattern having a persistentassignment followed by two non-persistent assignments. The persistentassignment is used for the first transmission of a packet, and theremaining assignments are for re-transmission as required. The secondaryassignment is shown in the bottom row. There is a repeating patternconsisting of a persistent assignment followed by two non-persistentassignments. The secondary assignment is available for furtherretransmissions of packets sent for the first time using the primaryassignment, but not yet successfully delivered after the availablenon-persistent assignments for re-transmission have been used. Asbefore, even though the first assignment is persistent, it can still beshared as described for previous embodiments.

In some embodiments, resources are persistently assigned to the firsttransmission of the primary but not the secondary assignments. Anexample is depicted in FIG. 21 which differs from FIG. 20 only in thatthere is no persistent assignment for the secondary assignment.

In some embodiments pertaining to systems with primary and secondaryresource assignments, it is useful to select the number of HARQtransmission to be twice the number of possible packet start points.

In some embodiments, some user groups of a given bitmap refer to userswith start positions of the first HARQ transmission of a sub-packet in agiven slot, and may be persistently assigned, while other user groups insame bitmap may not be persistently assigned.

In some embodiments, the presence of a secondary first slot persistentassignment may require the wireless station to monitor the secondarychannel as described in the previous embodiments. This may lead to twomodes of operation:

1) Jitter protection and high QOS—Attempt to receive secondaryassignment for each possible packet transmission. Send NAK and keep ifundecodable. The user will store the information and use it the decodingattempts of further transmissions until 1) the user identifies thepacket is not intended for it by assignment signalling (bitmap orotherwise) or another means, 2) the packet finishes the maximum numberof transmissions and/or 3) the packet is decoded successfully. (see theexamples of FIG. 20 or 21).

2) Re-transmission protection. (for example FIG. 21)

In some embodiments, the secondary resource is only used when needed dueto re-transmissions being exhausted on the primary channel, as in theexample of FIG. 20. This reduces the need to check secondary resources.

Supplementing a Bitmap Resource with Non-Persistent Assignment

In some embodiments, a given wireless station may be assigned a bitmapposition. This bitmap position may be a secondary assignment in additionto a primary bitmap position. The secondary assignment position in thebitmap may be assigned to only the given wireless station, or may beshared with the secondary bitmap location for other wireless stations.In some embodiments, the primary and secondary position(s) are on thesame bitmap and may correspond to the same user group.

In some embodiments, the secondary assignment(s) can be used tosupplement the resources assigned to a user for the purpose of aconcurrent sub-packet transmission.

In some embodiments, the primary and secondary assignment(s) may providea benefit to system performance in the presence of feedback errors.

In some embodiments, supplementing a bitmap resource with non-persistentassignment involves supplementing only when needed for concurrent packettransmissions at the interlace offset corresponding to a wirelessstation or a user group the wireless station belongs to.

The wireless station may be assigned a secondary bit location within thesame user group. This secondary bit location can collide with anotherwireless station's primary bit location. In some embodiments, multiplewireless stations share the same secondary bit location.

When the wireless station sends an ACK (acknowledgement) for a thirdHARQ transmission, the wireless station may not monitor the secondarybit location.

In a case where an NAK (negative acknowledgement) is detected by the BSinstead of an intended ACK (ACK-to-NAK error), the BS transmits a newpacket on the secondary bit location. In some embodiments, the wirelessstation may perform hypothesis testing to determine of there is anACK-to-NAK error on the primary location. If an ACK-to-NAK error isdetermined, then the wireless station will monitor the secondary bitlocation.

In some embodiments, the sub-packet sent on the wireless station'ssecondary bit location may not be for the wireless station. The wirelessstation is unable to decode the transmission, and thus keeps sendingNAKs. The wireless station assumes the secondary bit location does notcontain a new packet until all the HARQ transmission trials of thecurrent packet have completed. This is appropriate since any new packetis started in the primary bit location.

When the wireless station sends a NAK for the third HARQ transmission,the wireless station will monitor the secondary bit location for a newpacket transmission.

The BS may send another wireless station's packet on the secondary bitlocation of a given wireless station. The given wireless station doesnot know that the secondary bit location is for another wireless stationand will fail in decoding the received transmission. The given wirelessstation keeps sending NAKs until a maximum number of allowedtransmissions is reached.

In the case of the NAK-to-ACK error (0.1% probability), the wirelessstation may still monitor the secondary bitmap assuming there may be newpacket transmission. The wireless station will fail decoding and sendNAKs until a maximum number of allowed transmissions is reached. On theBS side, the BS will transmit a new packet on the primary bit location.The handling of NAK-to-ACK error detection on a primary bit location issimilar to a baseline case where the wireless station is only assigned aprimary bit location. The wireless station performs hypothesis testingto decide if a sub-packet transmitted on its designated interlace offsetis a sub-packet for a new transmission or retransmission.

In some embodiments, the first transmission of a packet at a given firstHARQ transmission opportunity may not be possible due to retransmissionsof other sub-packets.

In some embodiments, the sub-packet is delayed and sent at the nextfirst HARQ transmission opportunity. In some cases, one or moresub-packets can be concatenated into a single physical layer packet.

In some embodiments, the resources assigned to a wireless station may besupplemented to allow transmission of a packet comprised of concatenatedpacket(s).

As an example, for a wireless station, if an interlace offset resourcecorresponding to the user group the wireless station belongs to isoccupied by retransmission of a another packet, a new packet will waituntil the next occurrence of the interlace offset corresponding to theuser group. In this case, at the next occurrence of the interlaceoffset, there may be more than one packet pending for transmission at abuffer. The BS can concatenate the multiple packets into one singlephysical layer packet for transmission to the wireless station. In thiscase, the amount of physical channel resource assigned to the wirelessstation may be supplemented.

In some embodiment, the secondary assignment(s) can be used tosupplement the resources assigned to a user for the purpose of a largerassignment for transmission of concatenated packets.

In some embodiments, an approach to supplement a resource to thewireless station for a particular interlace offset corresponding to theuser group is by assigning a secondary bit location(s) to the wirelessstation.

It is to be understood that while a primary and a secondary bit locationand primary and secondary resources have been discussed, it is possiblethat there are additional bit locations and/or resources beyond theprimary and secondary. Furthermore, a secondary assignment may be usedwithout a primary assignment.

Since there are no concurrent transmissions, the supplement resourceindicated by the secondary bit location(s) is only present when AN sendsa new packets to the AT, i.e. when the HARQ transmissions of currentpacket have completed.

Allocation of Unused Resources

Embodiments have been described above in which a grouped resourceassignment is used to assign resources to members of a group from a setof resources within a group of shared resources. An example of this is agroup of resources that are assigned to users by a bitmap. Someresources within a shared resource may be unused in a given slot. Theunused resources may be contiguous or non-contiguous. The boundary of ashared resource segment maybe fixed or stationary. The unused resourcesof the shared resource can be used to send sub-packets to the wirelessstation. The sub-packets sent on the shared resource can be combinedwith the sub-packets sent on the non-shared resource to aid in decodingthe packet.

In some embodiments, the assignment of non-shared resources to wirelessstations may be performed utilizing unicast signalling messages andproper reception of transmissions or portions of transmissions usingunused shared resources may require information from a shared resourceallocation scheme, such as a bitmap.

The unused resources may be assigned to:

a wireless station notified by a signalling scheme, such as a unicastsignalling message;

a wireless station that is designated to use the unused resources ofthis shared resource segment or segments;

one or more wireless stations may be designated to use unused portionsof one or more shared resource segments

In some embodiments, the base station can choose to assign resources inaddition to the unused resources. These additional resources can beoutside the shared resource segment(s).

In some embodiments, the transmission is divided such that reception ofthe portion inside the shared resource will facilitate proper receptionof the transmission.

In some embodiments, the portion of the transmission sent within theshared resource space is chosen such that if the intended wirelessstation cannot receive it, reception of the packet can proceed withoutit, that is the portion of the transmission outside the shared resourcearea can be decoded.

A turbo encoded packet (possibly after interleaving, and permuting) canbe considered to be a vector of encoded symbols. A portion of thisvector may be transmitted during each HARQ transmission. Once theminimum code rate of the encoder is reached, further HARQ transmissionmay consist, in whole or in part, of repetitions of the previouslytransmitted encoded symbols.

The vector of encoded symbols can be thought of as placed on thecircumference of a circle. Each consecutive HARQ transmission is asegment of this circle, proceeding around the circumference. After allsegments of the circumference have been transmitted, the segments beginto contain repetitions of the segments of the circumference.

The encoded symbols can be transmitted in one of several modes. Forexample, in a first mode the encoded symbols are transmitted over bothshared and non-shared resources and in a second mode the encoded symbolsare transmitted over only a shared resource.

MODE 1: In some embodiments, the encoded symbols transmitted over thenon-shared resource for each HARQ transmission have a specific startingpoint, in the analogy described above a particular starting point alongthe circumference of the circle. Similarly, the encoded symbolstransmitted over the shared resource for each HARQ transmission have aspecific starting point along the circumference of the circle of encodedpackets.

In some embodiments, the encoded symbols of the first HARQ transmissiontransmitted over the non-shared resources may start at a particularposition, possibly starting with the transmission of systematic bits.The systematic bits are the data bits prior to being encoded with paritybits. Referring again to the analogy of the circle described above, theencoded symbols transmitted over the shared resources for the first HARQtransmission start from the same point on the circle, but are taken fromaround the circumference in the opposite direction.

The segments of the HARQ transmissions over non-shared resource portionsmay be contiguous segments of the vector of encoded symbols.

In some embodiments, the transmission start points of segments of theHARQ transmissions over shared resource portions are separated by themaximum size of a transmission of the shared resource for that wirelessstation. Having a fixed duration between start points in this mannerresults in the wireless station always being aware of the location ofthe next starting point for a transmission transmitted over sharedresource.

Start points for the portions transmitted over shared resources areassociated with HARQ transmission of the packet, and not necessarily thenumber of HARQ transmissions over the shared resources, as assignmentsusing shared resources may not be used for every transmission.

MODE 2: In some embodiments, it may be advantageous to transmit thewhole packet using only shared resources. The wireless terminal can besignalled by unicast signalling methods, or as part of the groupedresource allocation scheme.

This can be beneficial if the available resources are large enough toaccommodate proper transmission of the desired packet.

Assignment Message and Resource Usage Bitmap

In some systems, an assignment message may be used to indicateassignment of resources. This assignment message may be used to assignresources in conjunction with a resource usage bitmap.

In some embodiments, the assignment message and resource usage bitmapmay be sent in a single bitmap, or separately.

In some embodiments, the resource usage bitmap has entries thatcorrespond with all or a subset of resources in the system. The entriesindicate which resources are available. More than one resource usagebitmap can be used.

In some embodiments, signalling of an assignment message may be in theform of an assignment bitmap. The assignment bitmap may contain entrieseach corresponding to a wireless station or group of wireless stations.A wireless station may also have multiple entries corresponding to it.

In some embodiments, the assignment bitmap indicates the wirelessstations for which a packet transmission is to start transmission. As anexample, the assignment bitmap indicates only wireless stations forwhich a packet transmission is to start transmission in a given slot.

In some embodiments, when a wireless station is assigned to a group, aunicast signalling message may be sent to the wireless station from thebase station. The signalling message may contain one or more of thefollowing types of information:

persistent resource assignment for one or multiple HARQ transmissions;

bit position or positions within the assignment bitmap;

a set of positions, one for each interlace offset corresponding to theHARQ transmissions which are not assigned a persistent resource;

size, modulation and coding schemes of the assignment bitmap and otherassociated bitmaps that the user needs to decode in order to identifythe resource allocation.

The number of transmission start points or interlace offsets may not beequal to the maximum number of HARQ transmissions allowed for a packet.An interlace offset can consist of a slot or group of slots.

As with some previously described embodiments, user groups can bedefined as having their first HARQ transmission in a given slot, or agroup of slots, or an interlace offset within a given HARQ interlace.The first HARQ transmission positions can be the same or different thanthe maximum number of HARQ transmissions of a packet.

In some embodiments, a wireless station can belong to one or more usergroups. The user groups may or may not be all in the same HARQinterlace.

In some embodiments, the assignment bitmap for a slot contains entriesfor wireless stations assigned to the corresponding user group orgroups.

In some embodiments, the wireless stations starting a transmission candetermine their resource locations from the resource usage bitmap andassignments to other wireless stations. As an example, the ‘first’assignment indicated in the assignment bitmap may be assigned to the‘first’ set of available resources indicated by the resource usagebitmap, and continue sequentially for all assignments.

In some embodiments, a wireless station is assigned to only one usergroup so that it is assigned one position, in a single assignmentbitmap. In this manner, if the number of HARQ transmissions is greaterthen the number of first HARQ transmission positions, a new packettransmission can be started on a different resource prior to an earlierpacket completing all HARQ transmissions. This new assignment does notrequire additional bitmap positions. In general, a new packettransmission to a given wireless station can be started each time theassignment bitmap that includes that wireless station is sent, and doesnot conflict with any ongoing packet transmission to that wirelessstation.

In some embodiments, if a wireless station is transmitted multiplepackets in the same interlace offset, the packets may be distributedacross composite time slots of the interlace offset. As an example, ifVoIP packets are being transmitted to a given wireless station in asingle interlace offset, and the interlace offset consists of twogrouped time slots, the packet transmissions may be multiplexed so thatdifferent transmissions are sent over resources in the two differenttime slots of the interlace offset.

In some embodiments, the assignment bitmap for user groups can be senton different interlaces or interlace offsets. When a packet transmissionis started, all further HARQ transmissions, as needed, may be completedon the same interlace. Other assignments can be made on other interlacesin order to reduce or prevent the processing on multiple incomingpackets in the same slot.

As an example, a wireless station may be assigned to a user group thatis assigned a first HARQ packet transmission in interlace 0, andinterlace offset 0 for a given VoIP frame. The packet transmission isstarted and remains in interlace 0 for all HARQ transmissions. In thenext VoIP frame for interlace offset 0, the assignment bitmap for thisgroup is in interlace 1. A new packet is started and stays in interlace1, and so on.

Shifting to different interlaces in a sequential pattern for differentVoIP frames, or cyclically shifting resources, is an example of a mannerof changing interlaces for different VoIP frames. Cyclically shiftingresources is an example of a manner that can also be used for changinginterlace offsets for different VoIP frames.

In some embodiments, a user group can be subdivided into more than oneuser group, such that more than one user group corresponds to a givenslot. For example, a user group can be divided into smaller user groupsbased on for example, similar user channel conditions, MCSs, or resourceallocation size.

In some embodiments, separate assignment messages, for example bitmaps,may be used for each user group associated with a given slot.

In some embodiments, one or more assignment messages, for examplebitmaps, are transmitted in a given slot along with one or more resourceusage bitmaps.

In some embodiments, in a given slot, one or more assignment bitmaps areused to indicate assigned wireless stations, and a single resource usagebitmap is used to indicate available resources in the system due to allassignments from bitmaps or otherwise. The resource usage bitmap may besent separately, or encoded with the assignment bitmap intended for thewireless stations with poorest channel conditions, or the assignmentbitmap intended to have the largest coverage.

As an example, a system can use three assignment bitmaps, each fordifferent geometry wireless stations, and a single resource usagebitmap. Wireless stations in the bitmap corresponding to the lowestgeometry would be sequential assigned resources by observing if they areassigned from the assignment bitmap. The resource for a given wirelessstation is located in the first available resource indicated by theresource usage bitmap, taking into account the resources assigned toother wireless stations in bitmap positions that are read first.

Assignment for wireless stations of the second bitmap would follow in asimilar manner, taking into account the resources already assigned tothe first assignment bitmap.

Assignment for wireless stations of the third bitmap would follow in asimilar manner, taking into account the resources already assigned tothe first and second assignment bitmaps.

In some embodiments, assignment messages are resource assignmentmessages generally intended for a single user, for example sharedcontrol channel messages (SCCH), and a single resource usage bitmap isused to indicate available resources in the system due to allassignments from bitmaps or otherwise.

In some embodiments, the resource usage bitmap may have entries for asubset of resources in the system, or may have entries for all resourcesin the system including those used for broadcast, assignment, andcontrol channel messages.

Method of Resolving Feedback Errors

In some embodiments, it is advantageous to have a system where themaximum number of allowed HARQ transmissions for a packet is not aninteger multiple of the number of interlace offsets. When the maximumnumber of allowed HARQ transmissions for a packet is not an integermultiple of the number of interlace offsets the wireless station candetermine and recover from possible feedback errors, as opposed to whenthe maximum number of allowed HARQ transmissions for a packet is aninteger multiple of the number of interlace offsets.

In some embodiments, if a negative acknowledgement (NAK) sent by thewireless station is mistaken for a positive acknowledgement (ACK), thesystem will be able to recover.

An example of recovering from a mistakenly determined ACK when awireless station sent a NAK will now be described in relation to FIG.30. In the specific example, a portion of a frame including multipletransmission resource is generally indicated at 3000. The portionincludes three interlaces, interlace ‘0’ 3010, interlace ‘1’ 3020,interlace ‘2’ 3030 each with three interlace offsets, interlace offset‘0’ 3040, interlace offset ‘1’ 3050, interlace offset ‘2’ 3060. Allowinga maximum five HARQ transmissions per packet will ensure recovery if aNAK is mistaken for an ACK by the transmitter after the thirdtransmission.

Transmission for a given wireless station is assigned to starttransmission of packets on the interlace offset 0 of interlace 0indicated at 3070. A first transmission is sent by the base station. Thewireless station does not successfully receive and decode the firsttransmission so it sends a NAK back to the base station. A firstre-transmission, a second transmission, is sent by the base station oninterlace 0, interlace offset 1 indicated at 3075. The wireless stationdoes not successfully receive and decode the second transmission so itsends a NAK back to the base station. A second re-transmission, a thirdtransmission is sent by the base station on interlace 0, interlaceoffset 2 indicated at 3080. The wireless station does not successfullyreceive and decode the third transmission so it sends a NAK back to thebase station, but the base station mistakenly determines the NAK is anACK. In response to the mistakenly determined ACK, the base stationsends a first transmission for a new packet on interlace 0, interlaceoffset 0 indicated at 3085. However, the wireless station expects afourth transmission in the form of a third re-transmission. The wirelessstation attempts to combine the first transmission of the new packetwith the first through third transmissions of the original packetunsuccessfully, and sends a NAK to the base station. In interlace 0,interlace offset 1, indicated at 3090 the base station sends a secondtransmission for the new packet, which the wireless stationunsuccessfully attempts to combine as a fifth transmission of theoriginal sub-packet and send a NAK to the base station. The base stationsends a third transmission for the new packet on interlace 0, interlaceoffset 2 indicated at 3095. At interlace 0, interlace offset 2 3095, thewireless station determines that an error has occurred as it should notbe receiving a sixth packet transmissions as only five transmissions areallowed. The wireless station clears its buffer and attempts to decodethe transmission received at interlace 0, interlace offset 2 3095 as thethird transmission of a new packet. The wireless station than proceedswith receiving further retransmissions for the new packet if necessary.

In some embodiments, a wireless station will employ multiple packetbuffers in order to recover from possible acknowledgment feedbackerrors, and receive packet based on multiple hypothesis as to theidentity of packet is being transmitted.

Referring again to the above example, after a NAK has been sent for thethird transmission in interlace 0, interlace offset 2 3095, a wirelessstation utilizes an additional packet buffer to store a possible newtransmission in case an error occurs, as well as combining thetransmission with previous ones in a manner consist with the fourthtransmission of a sub-packet. In the next interlace, the transmission iscombined as the fifth transmission of the sub-packet in the main buffer,and as the second transmission of a new packet in the additional packetbuffer. In this manner, after determination that an error occurred ininterlace 0, interlace offset 2 3095, the wireless station can discardits main buffer and continue receiving and combining transmissions ofnew packets in its additional packet buffer.

In another example, allowing a maximum seven HARQ transmissions perpacket will ensure recovery if a NAK is mistaken for an ACK by thetransmitter after the third transmission.

In some embodiments, in a similar fashion to the above example, if apositive acknowledgement (ACK) sent by the wireless station is mistakenfor a negative acknowledgement (NAK), the system will be able torecover. For the purposes of providing context for embodiments of theinvention for use in a communication system, FIG. 4 shows a base stationcontroller (BSC) 10 which controls wireless communications withinmultiple cells 12, which cells are served by corresponding base stations(BS) 14. In general, each base station 14 facilitates communicationsusing OFDM with mobile and/or wireless terminals 16, which are withinthe cell 12 associated with the corresponding base station 14. Themovement of the mobile terminals 16 in relation to the base stations 14results in significant fluctuation in channel conditions. Asillustrated, the base stations 14 and mobile terminals 16 may includemultiple antennas to provide spatial diversity for communications.

With reference to FIG. 5, an example of a base station 14 isillustrated. The base station 14 generally includes a control system 20,a baseband processor 22, transmit circuitry 24, receive circuitry 26,multiple antennas 28, and a network interface 30. The receive circuitry26 receives radio frequency signals bearing information from one or moreremote transmitters provided by mobile terminals 16 (illustrated in FIG.4). A low noise amplifier and a filter (not shown) may cooperate toamplify and remove broadband interference from the signal forprocessing. Downconversion and digitization circuitry (not shown) willthen downconvert the filtered, received signal to an intermediate orbaseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another mobile terminal 16 serviced bythe base station 14.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by a carrier signal having a desiredtransmit frequency or frequencies. A power amplifier (not shown) willamplify the modulated carrier signal to a level appropriate fortransmission, and deliver the modulated carrier signal to the antennas28 through a matching network (not shown). Modulation and processingdetails are described in greater detail below.

With reference to FIG. 6, an example of a mobile terminal 16 isillustrated. Similarly to the base station 14, the mobile terminal 16will include a control system 32, a baseband processor 34, transmitcircuitry 36, receive circuitry 38, multiple antennas 40, and userinterface circuitry 42. The receive circuitry 38 receives radiofrequency signals bearing information from one or more base stations 14.A low noise amplifier and a filter (not shown) may cooperate to amplifyand remove broadband interference from the signal for processing.Downconversion and digitization circuitry (not shown) will thendownconvert the filtered, received signal to an intermediate or basebandfrequency signal, which is then digitized into one or more digitalstreams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 34 receives digitized data,which may represent voice, data, or control information, from thecontrol system 32, which it encodes for transmission. The encoded datais output to the transmit circuitry 36, where it is used by a modulatorto modulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to the antennas 40 through a matching network(not shown). Various modulation and processing techniques available tothose skilled in the art are used for signal transmission between themobile terminal and the base station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OEDM modulationis that orthogonal carrier waves are generated for multiple bands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

In operation, OFDM is preferably used for at least downlink transmissionfrom the base stations 14 to the mobile terminals 16. Each base station14 is equipped with “n” transmit antennas 28 (n>=1), and each mobileterminal 16 is equipped with “m” receive antennas 40 (m>=1). Notably,the respective antennas can be used for reception and transmission usingappropriate duplexers or switches and are so labelled only for clarity.

With reference to FIG. 7, a logical OFDM transmission architecture willbe described. Initially, the base station controller 10 will send datato be transmitted to various mobile terminals 16 to the base station 14.The base station 14 may use the channel quality indicators (CQIs)associated with the mobile terminals to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be directly from themobile terminals 16 or determined at the base station 14 based oninformation provided by the mobile terminals 16. In either case, the CQIfor each mobile terminal 16 is a function of the degree to which thechannel amplitude (or response) varies across the OFDM frequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile terminal 16. Again, thechannel coding for a particular mobile terminal 16 is based on the CQI.In some implementations, the channel encoder logic 50 uses known Turboencoding techniques. The encoded data is then processed by rate matchinglogic 52 to compensate for the data expansion associated with encoding.

Bit interleaver logic 54 systematically reorders the bits in the encodeddata to minimize the loss of consecutive data bits. The resultant databits are systematically mapped into corresponding symbols depending onthe chosen baseband modulation by mapping logic 56. Preferably,Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key(QPSK) modulation is used. The degree of modulation is preferably chosenbased on the CQI for the particular mobile terminal. The symbols may besystematically reordered to further bolster the immunity of thetransmitted signal to periodic data loss caused by frequency selectivefading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile terminal 16. The STC encoder logic60 will process the incoming symbols and provide “n” outputscorresponding to the number of transmit antennas 28 for the base station14. The control system 20 and/or baseband processor 22 as describedabove with respect to FIG. 5 will provide a mapping control signal tocontrol STC encoding. At this point, assume the symbols for the “n”outputs are representative of the data to be transmitted and capable ofbeing recovered by the mobile terminal 16.

For the present example, assume the base station 14 has two antennas 28(n=2) and the STC encoder logic 60 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 60 is sent to a corresponding IFFT processor 62,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 62 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 62 provides symbols in thetime domain. The time domain symbols are grouped into frames, which areassociated with a prefix by prefix insertion logic 64. Each of theresultant signals is up-converted in the digital domain to anintermediate frequency and converted to an analog signal via thecorresponding digital up-conversion (DUC) and digital-to-analog (D/A)conversion circuitry 66. The resultant (analog) signals are thensimultaneously modulated at the desired RF frequency, amplified, andtransmitted via the RF circuitry 68 and antennas 28. Notably, pilotsignals known by the intended mobile terminal 16 are scattered among thesub-carriers. The mobile terminal 16, which is discussed in detailbelow, will use the pilot signals for channel estimation.

Reference is now made to FIG. 8 to illustrate reception of thetransmitted signals by a mobile terminal 16. Upon arrival of thetransmitted signals at each of the antennas 40 of the mobile terminal16, the respective signals are demodulated and amplified bycorresponding RF circuitry 70. For the sake of conciseness and clarity,only one of the two receive paths is described and illustrated indetail. Analog-to-digital (A/D) converter and down-conversion circuitry72 digitizes and downconverts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 74 to control the gain of the amplifiers in the RFcircuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 76 includes frequency offset and clock estimationlogic 82, which is based on the headers to help estimate such effects onthe transmitted signal and provide those estimations to the correctionlogic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. Continuingwith FIG. 8, the processing logic compares the received pilot symbolswith the pilot symbols that are expected in certain sub-carriers atcertain times to determine a channel response for the sub-carriers inwhich pilot symbols were transmitted. The results are interpolated toestimate a channel response for most, if not all, of the remainingsub-carriers for which pilot symbols were not provided. The actual andinterpolated channel responses are used to estimate an overall channelresponse, which includes the channel responses for most, if not all, ofthe sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbolde-interleaver logic 102, which corresponds to the symbol interleaverlogic 58 of the transmitter. The de-interleaved symbols are thendemodulated or de-mapped to a corresponding bitstream using de-mappinglogic 104. The bits are then de-interleaved using bit de-interleaverlogic 106, which corresponds to the bit interleaver logic 54 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 108 and presented to channel decoder logic 110 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 112 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 114 forde-scrambling using the known base station de-scrambling code to recoverthe originally transmitted data 116.

In parallel to recovering the data 116, a CQI, or at least informationsufficient to create a CQI at the base station 14, is determined andtransmitted to the base station 14. As noted above, the CQI may be afunction of the carrier-to-interference ratio (CR), as well as thedegree to which the channel response varies across the varioussub-carriers in the OFDM frequency band. For this embodiment, thechannel gain for each sub-carrier in the OFDM frequency band being usedto transmit information is compared relative to one another to determinethe degree to which the channel gain varies across the OFDM frequencyband. Although numerous techniques are available to measure the degreeof variation, one technique is to calculate the standard deviation ofthe channel gain for each sub-carrier throughout the OFDM frequency bandbeing used to transmit data.

FIGS. 4 to 8 provide one specific example of a communication system thatcould be used to implement embodiments of the invention. It is to beunderstood that embodiments of the invention can be implemented withcommunications systems having architectures that are different than thespecific example, but that operate in a manner consistent with theimplementation of the embodiments as described herein.

FIG. 28 is a block diagram of an example of a base station that performsscheduling for downlink transmissions. A scheduler 504 is shown. Packetsto schedule 502 are shown, these having been received from a network500. This may include original sub-packets and/or retransmissionsub-packets in respect of packets to transmit. The scheduler 504 hasaccess to the packets, either through a physical connection or access tostored memory. The scheduler 504 also receives feedback 505 fromreceivers indicating whether or not transmissions have been successful.On the basis of the feedback 505 the scheduler 504 makes resourceallocation decisions and signals these to a signalling informationgenerator 506 which generates signalling information. This signallinginformation can take the form of any of any of the examples describedherein. The decisions are also communicated to frame generator 508 whichis responsible for taking the resource allocation decisions, andconstructing OFDM frames accordingly. In some embodiments, the OFDMframes will include the signalling information itself in which casedotted path 507 is implemented which represents the communication of thesignalling information from the signalling information generator 506 tothe frame generator 508, but alternatively separate channels for thesignalling information will be employed in which case path 509 isimplemented which represents the independent communication of thesignalling information. RF front end 510 prepares signals fortransmission using one or more antennas 512, depending on theimplementation. Feedback 505 is shown originating from the RF front end510, but there may be additional intervening components that performprocessing on received signals in order to generate the feedback 505.

A specific arrangement of components has been shown with specificinterconnections. It is to be understood that these functions may beimplemented in any suitable way, and that physical interconnections maybe implemented as logical connections/relationships.

FIG. 29 is an example of a receiver, such as a wireless station thatreceives and decodes sub-packets transmitted using one or more of theabove-described methods. Shown is an RF front end 600 with one or moreantennas 602, depending on the implementation. A signalling informationdecoder 604 extracts signalling channels from received signals anddetermines whether a resource has been scheduled for that receiver, andif so where. This can involve looking at whatever signalling isnecessary to deduce where the current sub-packet for that receiver islocated. Many detailed examples have been presented above. Havingdetermined where the sub-packet is, the sub-packet extraction module 606extracts the relevant parts from the received OFDM symbol stream, andpasses these on to packet decoder 608. Where multiple sub-packets for agiven packet have been received, these are used in combination toperform the decoding operation.

Structures, methods and features of various embodiments of the inventionhave been described separately, however in many combinations of theindividual structures, methods and features may exist.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1. A base station comprising: a scheduler to schedule packets fortransmission; a signalling information generator to generate signallinginformation based on information received from the scheduler; a framegenerator to construct frames based on information from the scheduler; atransmitter to transmit the frames; a receiver to receive feedback toaid in determining whether the transmitted frames were successfullyreceived.
 2. The base station of claim 1, wherein the scheduler receivesthe feedback from the receiver and utilizes the feedback to schedulepackets.
 3. The base station of claim 1, wherein the scheduler hasaccess to the packets through a physical connection.
 4. The base stationof claim 1, wherein the scheduler has access to the packets by accessinga stored memory
 5. The base station of claim 1, wherein frames generatedby the frame generator include signalling information from thesignalling information generator.
 6. A method for performingtransmission, comprising: scheduling a plurality of packets fortransmission; generating signalling information based on saidscheduling; generating a plurality frames for transmission based on saidscheduling; transmitting the plurality of frames; and receiving feedbackindicating whether the transmitted frames were successfully received. 7.The method of claim 5, further comprising: scheduling a second pluralityof packets for transmission based on the feedback.
 8. The method ofclaim 5, wherein said generating the plurality of frames is based on thesignalling information.
 9. The method of claim 8, wherein the pluralityof frames comprise the signalling information.
 10. The method of claim5, wherein the plurality of frames comprise a plurality of sub-packetscorresponding to the plurality of packets.
 11. The method of claim 10,wherein multiple sub-packets for a given packet are usable incombination to decode at least a portion of the signalling information.12. A non-transitory, computer accessible memory medium storing programinstructions for performing transmission, wherein the programinstructions are executable by one or more processors to: schedule aplurality of packets for transmission; generate signalling informationbased on said scheduling; generate a plurality frames for transmissionbased on said scheduling; transmit the plurality of frames; and receivefeedback indicating whether the transmitted frames were successfullyreceived.
 13. The non-transitory, computer accessible memory medium ofclaim 12, wherein the program instructions are further executable to:schedule a second plurality of packets for transmission based on thefeedback.
 14. The non-transitory, computer accessible memory medium ofclaim 12, wherein said generating the plurality of frames is based onthe signalling information.
 15. The non-transitory, computer accessiblememory medium of claim 12, wherein the plurality of frames comprise thesignalling information.
 16. The non-transitory, computer accessiblememory medium of claim 12, wherein the plurality of frames comprise aplurality of sub-packets corresponding to the plurality of packets,wherein multiple sub-packets for a given packet are usable incombination to decode at least a portion of the signalling information.17. A wireless station comprising: a receiver to receiver frames; asignalling information decoder to extract signalling channels fromreceived frame and determine whether a resource has been scheduled forthe wireless station, and if so where; a sub-packet extraction module toextract signalling channels from the received frames; a packet decoderto decode information on the signalling channels; a transmitter to sendfeedback indicating whether the transmitted frames were successfullydecoded.
 18. The wireless station of claim 17, wherein when multiplesub-packets for a given packet have been received, the multiplesub-packets are used in combination by the packet decoder to decode theinformation on the signalling channels.
 19. A method for performingreception, comprising: a wireless station receiving a plurality offrames; the wireless station extracting signalling channels from theplurality of frames; the wireless station determining resourcesscheduled for the wireless station; the wireless station decodinginformation on the signalling channels; the wireless stationtransmitting feedback indicating whether the plurality of frames weresuccessfully decoded based on said decoding.
 20. The method of claim 18,further comprising: wherein when multiple sub-packets for a given packethave been received, the multiple sub-packets are used in combination toperform said decoding the information on the signalling channels